gnulib: Ensure all libraries are used when building gdb/gdbserver

An issue was reported here related to building GDB on MinGW:

  https://sourceware.org/pipermail/gdb/2020-September/048927.html

It was suggested here:

  https://sourceware.org/pipermail/gdb/2020-September/048931.html

that the solution might be to make use of $(LIB_GETRANDOM), a variable
defined in the gnulib makefile, when linking GDB.

In fact I think the issue is bigger than just LIB_GETRANDOM.  When
using the script binutils-gdb/gnulib/update-gnulib.sh to reimport
gnulib there is a lot of output from gnulib's gnulib-tool.  Part of
that output is this:

  You may need to use the following makefile variables when linking.
  Use them in <program>_LDADD when linking a program, or
  in <library>_a_LDFLAGS or <library>_la_LDFLAGS when linking a library.
    $(FREXPL_LIBM)
    $(FREXP_LIBM)
    $(INET_NTOP_LIB)
    $(LIBTHREAD)
    $(LIB_GETLOGIN)
    $(LIB_GETRANDOM)
    $(LIB_HARD_LOCALE)
    $(LIB_MBRTOWC)
    $(LIB_SETLOCALE_NULL)
    $(LTLIBINTL) when linking with libtool, $(LIBINTL) otherwise

What I think this is telling us is that we should be including the
value of all these variables on the link line for gdb and gdbserver.

The problem though is that these variables are define in gnulib's
makefile, but are not (necessarily) defined in GDB's makefile.

One solution would be to recreate the checks that gnulib performs in
order to recreate these variables in both gdb's and gdbserver's
makefile.  Though this shouldn't be too hard, most (if not all) of
these checks are in the form macros defined in m4 files in the gnulib
tree, so we could just reference these as needed.  However, in this
commit I propose a different solution.

Currently, in the top level makefile, we give gdb and gdbserver a
dependency on gnulib.  Once gnulib has finished building gdb and
gdbserver can start, these projects then have a hard coded (relative)
path to the compiled gnulib library in their makefiles.

In this commit I extend the gnulib configure script to install a new
makefile fragment in the gnulib build directory.  This new file will
have the usual variable substitutions applied to it, and so can
include the complete list (see above) of all the extra libraries that
are needed when linking against gnulib.

In fact the new makefile fragment defines three variables, these are:

LIBGNU: The path to the archive containing gnulib.  Can be used as a
       dependency as when this file changes gdb/gdbserver should be
       relinked.

LIBGNU_EXTRA_LIBS: A list of linker -l.... flags that should be
       included in the link line of gdb/gdbserver.  These are
       libraries that $(LIBGNU) depends on.  This list is taken from
       the output of gnulib-tool, which is run by our
       gnulib/update-gnulib.sh script.

INCGNU: A list of -I.... include paths that should be passed to the
       compiler, these are where the gnulib headers can be found.

Now both gdb and gdbserver can include the makefile fragment and make
use of these variables.

The makefile fragment relies on the variable GNULIB_BUILDDIR being
defined.  This is checked for in the fragment, and was already defined
in the makefiles of gdb and gdbserver.

gdb/ChangeLog:

	* Makefile.in: Include Makefile.gnulib.inc.  Don't define LIBGNU
	or INCGNU.  Make use of LIBGNU_EXTRA_LIBS when linking.

gdbserver/ChangeLog:

	* Makefile.in: Include Makefile.gnulib.inc.  Don't define LIBGNU
	or INCGNU.  Make use of LIBGNU_EXTRA_LIBS when linking.

gnulib/ChangeLog:

	* Makefile.gnulib.inc.in: New file.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Install the new file.

9 files changed, 77 insertions, 10 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4927c89..75fdfeb 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2020-10-09  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* Makefile.in: Include Makefile.gnulib.inc.  Don't define LIBGNU
+	or INCGNU.  Make use of LIBGNU_EXTRA_LIBS when linking.
+
 2020-10-09  Jan Vrany  <jan.vrany@labware.com>
 
 	* source.c (directory_command): Notify observers that "directories"
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 80b788c..5f92e87 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -243,8 +243,7 @@ GDBFLAGS =
 
 # Helper code from gnulib.
 GNULIB_BUILDDIR = ../gnulib
-LIBGNU = $(GNULIB_BUILDDIR)/import/libgnu.a
-INCGNU = -I$(srcdir)/../gnulib/import -I$(GNULIB_BUILDDIR)/import
+include $(GNULIB_BUILDDIR)/Makefile.gnulib.inc
 
 SUPPORT = ../gdbsupport
 LIBSUPPORT = $(SUPPORT)/libgdbsupport.a
@@ -632,7 +631,7 @@ CLIBS = $(SIM) $(READLINE) $(OPCODES) $(LIBCTF) $(BFD) $(ZLIB) \
 	$(XM_CLIBS) $(GDBTKLIBS) \
 	@LIBS@ @GUILE_LIBS@ @PYTHON_LIBS@ \
 	$(LIBEXPAT) $(LIBLZMA) $(LIBBABELTRACE) $(LIBIPT) \
-	$(WIN32LIBS) $(LIBGNU) $(LIBICONV) \
+	$(WIN32LIBS) $(LIBGNU) $(LIBGNU_EXTRA_LIBS) $(LIBICONV) \
 	$(LIBMPFR) $(SRCHIGH_LIBS) $(LIBXXHASH) $(PTHREAD_LIBS) \
 	$(DEBUGINFOD_LIBS)
 CDEPS = $(NAT_CDEPS) $(SIM) $(BFD) $(READLINE_DEPS) $(CTF_DEPS) \
diff --git a/gdbserver/ChangeLog b/gdbserver/ChangeLog
index 510cf2e..262ceff 100644
--- a/gdbserver/ChangeLog
+++ b/gdbserver/ChangeLog
@@ -1,3 +1,8 @@
+2020-10-09  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* Makefile.in: Include Makefile.gnulib.inc.  Don't define LIBGNU
+	or INCGNU.  Make use of LIBGNU_EXTRA_LIBS when linking.
+
 2020-10-08  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* linux-low.cc (linux_process_target::handle_extended_wait):
diff --git a/gdbserver/Makefile.in b/gdbserver/Makefile.in
index c8cfed4..1969ed0 100644
--- a/gdbserver/Makefile.in
+++ b/gdbserver/Makefile.in
@@ -114,8 +114,7 @@ ustinc = @ustinc@
 
 # gnulib
 GNULIB_BUILDDIR = ../gnulib
-LIBGNU = $(GNULIB_BUILDDIR)/import/libgnu.a
-INCGNU = -I$(srcdir)/../gnulib/import -I$(GNULIB_BUILDDIR)/import
+include $(GNULIB_BUILDDIR)/Makefile.gnulib.inc
 
 # Where is the INTL library?  Typically in ../intl.
 INTL = @LIBINTL@
@@ -360,8 +359,8 @@ gdbserver$(EXEEXT): $(sort $(OBS)) ${CDEPS} $(LIBGNU) $(LIBIBERTY) \
 	$(ECHO_CXXLD) $(CC_LD) $(INTERNAL_CFLAGS) $(INTERNAL_LDFLAGS) \
 		$(CXXFLAGS) \
 		-o gdbserver$(EXEEXT) $(OBS) $(GDBSUPPORT) $(LIBGNU) \
-		$(LIBIBERTY) $(INTL) $(GDBSERVER_LIBS) $(XM_CLIBS) \
-		$(WIN32APILIBS)
+		$(LIBGNU_EXTRA_LIBS) $(LIBIBERTY) $(INTL) \
+		$(GDBSERVER_LIBS) $(XM_CLIBS) $(WIN32APILIBS)
 
 gdbreplay$(EXEEXT): $(sort $(GDBREPLAY_OBS)) $(LIBGNU) $(LIBIBERTY) \
 		$(INTL_DEPS) $(GDBSUPPORT)
@@ -369,8 +368,8 @@ gdbreplay$(EXEEXT): $(sort $(GDBREPLAY_OBS)) $(LIBGNU) $(LIBIBERTY) \
 	$(ECHO_CXXLD) $(CC_LD) $(INTERNAL_CFLAGS) $(INTERNAL_LDFLAGS) \
 		$(CXXFLAGS) \
 		-o gdbreplay$(EXEEXT) $(GDBREPLAY_OBS) $(XM_CLIBS) \
-		$(GDBSUPPORT) $(LIBGNU) $(LIBIBERTY) $(INTL) \
-		$(WIN32APILIBS)
+		$(GDBSUPPORT) $(LIBGNU) $(LIBGNU_EXTRA_LIBS) \
+		$(LIBIBERTY) $(INTL) $(WIN32APILIBS)
 
 IPA_OBJS = \
 	alloc-ipa.o \
diff --git a/gnulib/ChangeLog b/gnulib/ChangeLog
index bf61742..909df78 100644
--- a/gnulib/ChangeLog
+++ b/gnulib/ChangeLog
@@ -1,3 +1,10 @@
+2020-10-09  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* Makefile.gnulib.inc.in: New file.
+	* Makefile.in: Regenerate.
+	* configure: Regenerate.
+	* configure.ac: Install the new file.
+
 2020-09-08  Tom Tromey  <tromey@adacore.com>
 
 	PR win32/25302:
diff --git a/gnulib/Makefile.gnulib.inc.in b/gnulib/Makefile.gnulib.inc.in
new file mode 100644
index 0000000..f3fd72b
--- /dev/null
+++ b/gnulib/Makefile.gnulib.inc.in
@@ -0,0 +1,44 @@
+# Copyright (C) 2020 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# A makefile snippet that lists all of the libraries that should be
+# pulled in when linking against gnulib.  Both GDB and GDBSERVER will
+# include this snippet.
+#
+# The defined variables are:
+#
+# LIBGNU: The path to the archive containing gnulib.  Can be used as a
+#        dependency as when this file changes gdb/gdbserver should be
+#        relinked.
+#
+# LIBGNU_EXTRA_LIBS: A list of linker -l.... flags that should be
+#        included in the link line of gdb/gdbserver.  These are
+#        libraries that $(LIBGNU) depends on.  This list is taken from
+#        the output of gnulib-tool, which is run by our
+#        gnulib/update-gnulib.sh script.
+#
+# INCGNU: A list of -I.... include paths that should be passed to the
+#        compiler, these are where the gnulib headers can be found.
+
+ifndef GNULIB_BUILDDIR
+$(error missing GNULIB_BUILDDIR)
+endif
+
+LIBGNU = $(GNULIB_BUILDDIR)/import/libgnu.a
+LIBGNU_EXTRA_LIBS = @FREXPL_LIBM@ @FREXP_LIBM@ @INET_NTOP_LIB@ \
+                    @LIBTHREAD@ @LIB_GETLOGIN@ @LIB_GETRANDOM@ \
+                    @LIB_HARD_LOCALE@ @LIB_MBRTOWC@ \
+                    @LIB_SETLOCALE_NULL@ @LIBINTL@
+INCGNU = -I$(srcdir)/../gnulib/import -I$(GNULIB_BUILDDIR)/import
diff --git a/gnulib/Makefile.in b/gnulib/Makefile.in
index bdd3c3f..c1c2168 100644
--- a/gnulib/Makefile.in
+++ b/gnulib/Makefile.in
@@ -277,7 +277,7 @@ am__CONFIG_DISTCLEAN_FILES = config.status config.cache config.log \
  configure.lineno config.status.lineno
 mkinstalldirs = $(SHELL) $(top_srcdir)/../mkinstalldirs
 CONFIG_HEADER = config.h
-CONFIG_CLEAN_FILES =
+CONFIG_CLEAN_FILES = Makefile.gnulib.inc
 CONFIG_CLEAN_VPATH_FILES =
 AM_V_P = $(am__v_P_@AM_V@)
 am__v_P_ = $(am__v_P_@AM_DEFAULT_V@)
@@ -1642,6 +1642,8 @@ $(srcdir)/config.in: @MAINTAINER_MODE_TRUE@ $(am__configure_deps)
 
 distclean-hdr:
 	-rm -f config.h stamp-h1
+Makefile.gnulib.inc: $(top_builddir)/config.status $(srcdir)/Makefile.gnulib.inc.in
+	cd $(top_builddir) && $(SHELL) ./config.status $@
 
 # This directory's subdirectories are mostly independent; you can cd
 # into them and run 'make' without going through this Makefile.
diff --git a/gnulib/configure b/gnulib/configure
index 5c6add6..6c58a46 100644
--- a/gnulib/configure
+++ b/gnulib/configure
@@ -30802,6 +30802,9 @@ fi
 # Checks for libraries.  #
 # ---------------------- #
 
+ac_config_files="$ac_config_files Makefile.gnulib.inc"
+
+
 ac_config_files="$ac_config_files Makefile import/Makefile"
 
 ac_config_commands="$ac_config_commands default"
@@ -31634,6 +31637,7 @@ do
   case $ac_config_target in
     "config.h") CONFIG_HEADERS="$CONFIG_HEADERS config.h:config.in" ;;
     "depfiles") CONFIG_COMMANDS="$CONFIG_COMMANDS depfiles" ;;
+    "Makefile.gnulib.inc") CONFIG_FILES="$CONFIG_FILES Makefile.gnulib.inc" ;;
     "Makefile") CONFIG_FILES="$CONFIG_FILES Makefile" ;;
     "import/Makefile") CONFIG_FILES="$CONFIG_FILES import/Makefile" ;;
     "default") CONFIG_COMMANDS="$CONFIG_COMMANDS default" ;;
diff --git a/gnulib/configure.ac b/gnulib/configure.ac
index acc1b1a..052b8bd 100644
--- a/gnulib/configure.ac
+++ b/gnulib/configure.ac
@@ -56,6 +56,8 @@ AC_CHECK_TOOL(AR, ar)
 # Checks for libraries.  #
 # ---------------------- #
 
+AC_CONFIG_FILES(Makefile.gnulib.inc)
+
 AC_OUTPUT(Makefile import/Makefile,
 [
 case x$CONFIG_HEADERS in