kbuild/btf: Propagate CONFIG_WERROR to resolve_btfids

Use CONFIG_WERROR to also fail on warnings emitted by resolve_btfids.
Allow the CI bots to prevent the introduction of new warnings.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20241204-resolve_btfids-v3-2-e6a279a74cfd@weissschuh.net