kbuild: install-extmod-build: Package resolve_btfids if necessary

kbuild: install-extmod-build: Package resolve_btfids if necessary

When CONFIG_DEBUG_INFO_BTF_MODULES is enabled and vmlinux is available,
Makefile.modfinal and gen-btf.sh will try to use resolve_btfids on the
module .ko. install-extmod-build currently does not package
resolve_btfids, so that step fails.

Package resolve_btfids if it may be used.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20260226-kbuild-resolve_btfids-v1-1-2bf38b93dfe7@linutronix.de
[nathan: Small commit message tweaks]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>