runtime/cgo: CFRelease result from CFBundleCopyResourceURL

The result from CFBundleCopyResourceURL is owned by the caller. This
CL adds the necessary CFRelease to release it after use.

Fixes #19722

Change-Id: I7afe22ef241d21922a7f5cef6498017e6269a5c3
Reviewed-on: https://go-review.googlesource.com/38639
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

src/runtime/cgo/gcc_darwin_arm.c

@@ -108,7 +108,9 @@ init_working_dir()
 	}
 	CFStringRef url_str_ref = CFURLGetString(url_ref);
 	char buf[MAXPATHLEN];
-	if (!CFStringGetCString(url_str_ref, buf, sizeof(buf), kCFStringEncodingUTF8)) {
+	Boolean res = CFStringGetCString(url_str_ref, buf, sizeof(buf), kCFStringEncodingUTF8);
+	CFRelease(url_ref);
+	if (!res) {
 		fprintf(stderr, "runtime/cgo: cannot get URL string\n");
 		return;
 	}

src/runtime/cgo/gcc_darwin_arm64.c

@@ -110,7 +110,9 @@ init_working_dir()
 	}
 	CFStringRef url_str_ref = CFURLGetString(url_ref);
 	char buf[MAXPATHLEN];
-	if (!CFStringGetCString(url_str_ref, buf, sizeof(buf), kCFStringEncodingUTF8)) {
+	Boolean res = CFStringGetCString(url_str_ref, buf, sizeof(buf), kCFStringEncodingUTF8);
+	CFRelease(url_ref);
+	if (!res) {
 		fprintf(stderr, "runtime/cgo: cannot get URL string\n");
 		return;
 	}