kbuild: dummy-tools: fix inverted tests for gcc

There is a test in Kconfig which takes inverted value of a compiler
check:
* config CC_HAS_INT128
        def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0)

This results in CC_HAS_INT128 not being in super-config generated by
dummy-tools. So take this into account in the gcc script.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

scripts/dummy-tools/gcc

@@ -85,3 +85,8 @@ if arg_contain -print-file-name=plugin "$@"; then
 	echo $plugin_dir
 	exit 0
 fi
+
+# inverted return value
+if arg_contain -D__SIZEOF_INT128__=0 "$@"; then
+	exit 1
+fi