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 <[e-mail]>
Reviewed-by: Nicolas Schier <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
[nathan: Small commit message tweaks]
Signed-off-by: Nathan Chancellor <[e-mail]>

scripts/package/install-extmod-build

···
 		echo tools/objtool/objtool
 	fi
 
+	if is_enabled CONFIG_DEBUG_INFO_BTF_MODULES; then
+		echo tools/bpf/resolve_btfids/resolve_btfids
+	fi
+
 	echo Module.symvers
 	echo "arch/${SRCARCH}/include/generated"
 	echo include/config/auto.conf