compilers: handle -Wno-attributes= for GCC

For other reasons, Meson transforms "-Wno-x" into "-Wx -Wno-x" for GCC,
but this breaks with "-Wno-attributes=x" with:
```
cc1plus: error: arguments ignored for '-Wattributes='; use '-Wno-attributes=' instead
```

Suppress that workaround for -Wno-attributes=.

Closes: mesonbuild#13022

mesonbuild/compilers/mixins/clike.py

@@ -1269,7 +1269,7 @@ def _has_multi_arguments(self, args: T.List[str], env: 'Environment', code: str)
             # some compilers, e.g. GCC, don't warn for unsupported warning-disable
             # flags, so when we are testing a flag like "-Wno-forgotten-towel", also
             # check the equivalent enable flag too "-Wforgotten-towel"
-            if arg.startswith('-Wno-'):
+            if arg.startswith('-Wno-') and not arg.startswith('-Wno-attributes='):
                 new_args.append('-W' + arg[5:])
             if arg.startswith('-Wl,'):
                 mlog.warning(f'{arg} looks like a linker argument, '

test cases/common/104 has arg/meson.build

@@ -52,6 +52,12 @@ if cc.get_id() == 'gcc'
   assert(not cc.has_multi_arguments(['-Wno-pragmas', '-Wno-lol-meson-test-flags']), 'should error out even if some -Wno args are valid')
 endif
 
+if cpp.get_id() == 'gcc' and cpp.version().version_compare('>=12.1.0')
+  # Handle special -Wno-attributes=foo where -Wattributes=foo is invalid
+  # i.e. our usual -Wno-foo -Wfoo hack doesn't work for -Wattributes=foo.
+  assert(cpp.has_argument('-Wno-attributes=meson::i_do_not_exist'))
+endif
+
 if cc.get_id() == 'clang' and cc.version().version_compare('<=4.0.0')
   # 4.0.0 does not support -fpeel-loops. Newer versions may.
   # Please adjust above version number as new versions of clang are released.