[gdb/testsuite] Fix gdb.fortran/info-modules.exp with gcc-4.8

When running test-case gdb.fortran/info-modules.exp with gfortran 4.8.5, I
get:
...
FAIL: gdb.fortran/info-modules.exp: info module functions: \
  check for entry 'info-types.f90', '35', \
  'void mod1::__copy_mod1_M1t1\(Type m1t1, Type m1t1\);'
FAIL: gdb.fortran/info-modules.exp: info module functions -m mod1: \
  check for entry 'info-types.f90', '35', \
  'void mod1::__copy_mod1_M1t1\(Type m1t1, Type m1t1\);'
FAIL: gdb.fortran/info-modules.exp: info module variables: \
  check for entry 'info-types.f90', '(35)?', \
  'Type m1t1 mod1::__def_init_mod1_M1t1;'
FAIL: gdb.fortran/info-modules.exp: info module variables: \
  check for entry 'info-types.f90', '(35)?', \
  'Type __vtype_mod1_M1t1 mod1::__vtab_mod1_M1t1;'
...

With gfortran 7.5.0, we have:
...
$ readelf -wi info-modules | egrep "DW_AT_name.*(copy|def_init|vtype)_mod1"
    <286>   DW_AT_name        : __def_init_mod1_M1t1
    <29f>   DW_AT_name        : __vtype_mod1_M1t1
    <3de>   DW_AT_name        : __copy_mod1_M1t1
$
...
but with gfortran 4.8.5:
...
$ readelf -wi info-modules | egrep "DW_AT_name.*(copy|def_init|vtype)_mod1"
$
...

Fix this by allowing these module functions and variables to be missing.

Tested on x86_64-linux with gcc 4.8.5 and gcc 7.5.0.

gdb/testsuite/ChangeLog:

2020-07-30  Tom de Vries  <tdevries@suse.de>

	* lib/sym-info-cmds.exp (GDBInfoModuleSymbols::check_entry_1): Factor
	out of ...
	(GDBInfoModuleSymbols::check_entry): ... here.
	(GDBInfoModuleSymbols::check_optional_entry): New proc.
	* gdb.fortran/info-modules.exp: Use check_optional_entry for entries
	related to __def_init_mod1_M1t1 / __vtype_mod1_M1t1 / __copy_mod1_M1t1.

1 files changed, 19 insertions, 2 deletions

diff --git a/gdb/testsuite/lib/sym-info-cmds.exp b/gdb/testsuite/lib/sym-info-cmds.exp
index 02f8b32..dd769ef 100644
--- a/gdb/testsuite/lib/sym-info-cmds.exp
+++ b/gdb/testsuite/lib/sym-info-cmds.exp
@@ -421,7 +421,10 @@ namespace eval GDBInfoModuleSymbols {
     # If a matching entry is found then it is removed from the
     # _entries list, this allows us to check for duplicates using the
     # check_no_entry call.
-    proc check_entry { filename module lineno text { testname "" } } {
+    #
+    # If OPTIONAL, don't generate a FAIL for a mismatch, but use UNSUPPORTED
+    # instead.
+    proc check_entry_1 { filename module lineno text optional testname } {
 	variable _entries
 	variable _last_command
 
@@ -458,7 +461,21 @@ namespace eval GDBInfoModuleSymbols {
 	}
 
 	set _entries $new_entries
-	gdb_assert { $found_match } $testname
+	if { $optional && ! $found_match } {
+	    unsupported $testname
+	} else {
+	    gdb_assert { $found_match } $testname
+	}
+    }
+
+    # Call check_entry_1 with OPTIONAL == 0.
+    proc check_entry { filename module lineno text { testname "" } } {
+	check_entry_1 $filename $module $lineno $text 0 $testname
+    }
+
+    # Call check_entry_1 with OPTIONAL == 1.
+    proc check_optional_entry { filename module lineno text { testname "" } } {
+	check_entry_1 $filename $module $lineno $text 1 $testname
     }
 
     # Check that there is no entry in the _entries list matching