gcc: fixed parse-config to only inject -fstack-protector if we have a proper compiler supporting it

Note:

At stage 0 (toolchain) we are building a static gcc with explicitely disabled
stack-smashing protection.

base/gcc/parse-config

@@ -18,7 +18,11 @@
 #
 if [ "${SDECFG_DEFAULT_CC:0:3}" = "gcc" -a "$SDECFG_PKG_GCC_STACKPRO" = 1 ]; then
 	if ! hasflag NO-SSP; then
-		var_append GCC_WRAPPER_INSERT ' ' '-fstack-protector'
+		if pkginstalled -f gcc; then
+			var_append GCC_WRAPPER_INSERT ' ' '-fstack-protector'
+		else
+			echo_warning 'Disabling GCC stack-protector (not supported by toolchain gcc)'
+		fi
 	else
 		echo_warning 'Package incompatible with GCC stack-protector, disabled'
 	fi