kbuild: dummy-tools: adjust to stricter stackprotector check

Commit 3fb0fdb3 ("x86/stackprotector/32: Make the canary into a regular
percpu variable") modified the stackprotector check on 32-bit x86 to check
if gcc supports using %fs as canary. Adjust dummy-tools gcc script to pass
this new test by returning "%fs" rather than "%gs" if it detects
-mstack-protector-guard-reg=fs on command line.

Fixes: 3fb0fdb3 ("x86/stackprotector/32: Make the canary into a regular percpu variable")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/dummy-tools/gcc

@@ -76,7 +76,11 @@ fi
 if arg_contain -S "$@"; then
 	# For scripts/gcc-x86-*-has-stack-protector.sh
 	if arg_contain -fstack-protector "$@"; then
+		if arg_contain -mstack-protector-guard-reg=fs "$@"; then
+			echo "%fs"
+		else
 			echo "%gs"
+		fi
 		exit 0
 	fi