rust: kbuild: add -fzero-init-padding-bits to bindgen_skip_cflags

[ Upstream commit a9c621a217128eb3fb7522cf763992d9437fd5ba ]

This seems to break the build when building with gcc15:

    Unable to generate bindings: ClangDiagnostic("error: unknown
    argument: '-fzero-init-padding-bits=all'\n")

Thus skip that flag.

Signed-off-by: Justin M. Forbes <jforbes@fedoraproject.org>
Fixes: dce4aab8441d ("kbuild: Use -fzero-init-padding-bits=all")
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20250129215003.1736127-1-jforbes@fedoraproject.org
[ Slightly reworded commit. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

rust/Makefile

@@ -229,6 +229,7 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
 	-fzero-call-used-regs=% -fno-stack-clash-protection \
 	-fno-inline-functions-called-once -fsanitize=bounds-strict \
 	-fstrict-flex-arrays=% -fmin-function-alignment=% \
+	-fzero-init-padding-bits=% \
 	--param=% --param asan-%
 
 # Derived from `scripts/Makefile.clang`.