gnome: initialize CFLAGS environment variable to linker arguments

The CFLAGS environment variable is used for g-ir-scanner's linking pass,
It is emptied since commit 237513d ("modules/gnome, modules/Python:
Allow injecting RPATH flags through LDFLAGS if needed", 2025-04-09);
which could even be considered a bugfix if it didn't break Fedora
quite badly.

I could not write a testcase, but the culprit seems to be the
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 that Fedora places
in CFLAGS.  The file contains

    *cc1_options:
    + %{!r:%{!fpie:%{!fPIE:%{!fpic:%{!fPIC:%{!fno-pic:-fPIE}}}}}}

and the lack of -fPIE option upsets the linker.  Fix by priming
the contents of the CFLAGS variable with the c_link_args being used
for the build.

Fixes: #14631
Signed-off-by: Paolo Bonzini <[email protected]>
(cherry picked from commit 6cf3120)

Author: bonzini

mesonbuild/modules/gnome.py

@@ -1168,7 +1168,7 @@ def generate_gir(self, state: 'ModuleState', args: T.Tuple[T.List[T.Union[Execut
         scan_cflags += list(self._get_scanner_cflags(self._get_external_args_for_langs(state, [lc[0] for lc in langs_compilers])))
         scan_internal_ldflags = []
         scan_external_ldflags = []
-        scan_env_ldflags = []
+        scan_env_ldflags = state.environment.coredata.get_external_link_args(MachineChoice.HOST, 'c')
         for cli_flags, env_flags in (self._get_scanner_ldflags(internal_ldflags), self._get_scanner_ldflags(dep_internal_ldflags)):
             scan_internal_ldflags += cli_flags
             scan_env_ldflags += env_flags