compile: Add 'set compile-gcc'

As discussed in
	How to use compile & execute function in GDB
	https://sourceware.org/ml/gdb/2015-04/msg00026.html

GDB currently searches for compilers on /usr/bin/ARCH-OS-gcc and
chooses a match from there.  However, it is not currently possible for
the user to override which compiler to use.  This is what this patch
implements.

It is also a sync between GCC's and GDB's interfaces.

gdb/ChangeLog
2017-08-23  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* NEWS (Changes since GDB 7.9): Add set compile-gcc and show
	compile-gcc.
	* compile/compile.c (compile_gcc, show_compile_gcc): New.
	(compile_to_object): Implement compile_gcc.
	(_initialize_compile): Install "set compile-gcc".  Initialize
	compile_gcc.

gdb/doc/ChangeLog
2017-08-23  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.texinfo (Compiling and Injecting Code): Add to subsection
	"Compiler search for the compile command" descriptions of set
	compile-gcc and show compile-gcc.

include/ChangeLog
2017-08-23  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gcc-interface.h (enum gcc_base_api_version): Update comment for
	GCC_FE_VERSION_1.
	(struct gcc_base_vtable): Rename set_arguments to set_arguments_v0.
	Add set_arguments, set_triplet_regexp and set_driver_filename.

2 files changed, 36 insertions, 6 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 40b0e40..bf82730 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,9 @@
+2017-08-23  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	* gdb.texinfo (Compiling and Injecting Code): Add to subsection
+	"Compiler search for the compile command" descriptions of set
+	compile-gcc and show compile-gcc.
+
 2017-08-07  Weimin Pan  <weimin.pan@oracle.com>
 
 	* gdb.texinfo (Architectures): Add new Sparc64 section to document
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index d0d5d96..d977b23 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -18154,13 +18154,15 @@ will print to the console.
 
 @subsection Compiler search for the @code{compile} command
 
-@value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
-may not be obvious for remote targets of different architecture than where
-@value{GDBN} is running.  Environment variable @code{PATH} (@code{PATH} from
-shell that executed @value{GDBN}, not the one set by @value{GDBN}
-command @code{set environment}).  @xref{Environment}.  @code{PATH} on
+@value{GDBN} needs to find @value{NGCC} for the inferior being debugged
+which may not be obvious for remote targets of different architecture
+than where @value{GDBN} is running.  Environment variable @code{PATH} on
 @value{GDBN} host is searched for @value{NGCC} binary matching the
-target architecture and operating system.
+target architecture and operating system.  This search can be overriden
+by @code{set compile-gcc} @value{GDBN} command below.  @code{PATH} is
+taken from shell that executed @value{GDBN}, it is not the value set by
+@value{GDBN} command @code{set environment}).  @xref{Environment}.
+
 
 Specifically @code{PATH} is searched for binaries matching regular expression
 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
@@ -18170,6 +18172,28 @@ example both @code{i386} and @code{x86_64} targets look for pattern
 for pattern @code{s390x?}.  @var{os} is currently supported only for
 pattern @code{linux(-gnu)?}.
 
+On Posix hosts the compiler driver @value{GDBN} needs to find also
+shared library @file{libcc1.so} from the compiler.  It is searched in
+default shared library search path (overridable with usual environment
+variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
+compile-gcc} settings.  Contrary to it @file{libcc1plugin.so} is found
+according to the installation of the found compiler --- as possibly
+specified by the @code{set compile-gcc} command.
+
+@table @code
+@item set compile-gcc
+@cindex compile command driver filename override
+Set compilation command used for compiling and injecting code with the
+@code{compile} commands.  If this option is not set (it is set to
+an empty string), the search described above will occur --- that is the
+default.
+
+@item show compile-gcc
+Displays the current compile command @value{NGCC} driver filename.
+If set, it is the main command @command{gcc}, found usually for example
+under name @file{x86_64-linux-gnu-gcc}.
+@end table
+
 @node GDB Files
 @chapter @value{GDBN} Files