toolchain/toolchain-wrapper: make gcc --help -v work correctly

make "gcc --help -v" display all the options, some packages depend on this
https://bugs.busybox.net/show_bug.cgi?id=15231

Signed-off-by: Sagi Mor <sagimor6@gmail.com>
[Arnout: move the handling to the beginning and directly call execv]
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
(cherry picked from commit 9954315fc5)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

toolchain/toolchain-wrapper.c

@@ -310,6 +310,17 @@ int main(int argc, char **argv)
 		perror(__FILE__ ": overflow");
 		return 3;
 	}
+
+	/* skip all processing --help is specified */
+	for (i = 1; i < argc; i++) {
+		if (!strcmp(argv[i], "--help")) {
+			argv[0] = path;
+			if (execv(path, argv))
+				perror(path);
+			return 1;
+		}
+	}
+
 #ifdef BR_CCACHE
 	ret = snprintf(ccache_path, sizeof(ccache_path), "%s/bin/ccache", absbasedir);
 	if (ret >= sizeof(ccache_path)) {