[PATCH 2/2] [gdb/testsuite] Use Wno-non-c-typedef-for-linkage for gcc 16

[Tom de Vries <tdevries@suse.de>]

With gcc 16 and test-case gdb.cp/classes.exp I run into:
...
classes.cc:440:15: warning: anonymous non-C-compatible type given name for linkage purposes by 'typedef' declaration [-Wnon-c-typedef-for-linkage]^M
  440 | typedef class {^M
      |               ^^M
      |               DynamicBase2^M
classes.cc:443:15: note: type is not C-compatible because it contains 'virtual int DynamicBase2::get_x()' declaration^M
  443 |   virtual int get_x () { return x; }^M
      |               ^~~~~^M
...

Fix this by applying Wno-non-c-typedef-for-linkage, which is already done for
clang.

Likewise for gdb.cp/class2.exp.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34187
---
 gdb/testsuite/gdb.cp/class2.exp  | 3 ++-
 gdb/testsuite/gdb.cp/classes.exp | 9 ++++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/gdb/testsuite/gdb.cp/class2.exp b/gdb/testsuite/gdb.cp/class2.exp
index 705f51ac3e0..aa2a04467f4 100644
--- a/gdb/testsuite/gdb.cp/class2.exp
+++ b/gdb/testsuite/gdb.cp/class2.exp
@@ -21,7 +21,8 @@ standard_testfile .cc
 set flags [list debug c++]
 # When using recent Clangs, this test fails to compile without this warning
 # being disabled.  However, older Clangs fail to recognize the flag.
-if { [gcc_major_version "clang-*" "c++"] > 10 } {
+if { [gcc_major_version "clang-*" "c++"] > 10
+     || [gcc_major_version "gcc-*" "c++"] >= 16} {
     lappend flags additional_flags=-Wno-non-c-typedef-for-linkage
 }
 
diff --git a/gdb/testsuite/gdb.cp/classes.exp b/gdb/testsuite/gdb.cp/classes.exp
index 71ce810adad..d2fb7c0c14c 100644
--- a/gdb/testsuite/gdb.cp/classes.exp
+++ b/gdb/testsuite/gdb.cp/classes.exp
@@ -25,12 +25,15 @@ load_lib "cp-support.exp"
 standard_testfile .cc
 
 set flags [list debug c++]
+
 set clang_used false
 if { [test_compiler_info "clang-*" "c++"] } {
     set clang_used true
-    if { [gcc_major_version "clang-*" "c++"] >= 11} {
-	lappend flags additional_flags=-Wno-non-c-typedef-for-linkage
-    }
+}
+
+if { [gcc_major_version "clang-*" "c++"] >= 11
+     || [gcc_major_version "gcc-*" "c++"] >= 16} {
+    lappend flags additional_flags=-Wno-non-c-typedef-for-linkage
 }
 
 if {[prepare_for_testing "failed to prepare" $testfile $srcfile $flags]} {
-- 
2.51.0