util: Always export default visibility.

This should fix the CFI build compatibility with class exports.

Bug: chromium:1030192
Bug: angleproject:3162
Change-Id: I228d6d387f8b29c0a500038de962f9f216454d7a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1964933
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

util/util_export.h

@@ -16,11 +16,7 @@
 #            define ANGLE_UTIL_EXPORT __declspec(dllimport)
 #        endif
 #    elif defined(__GNUC__)
-#        if defined(LIBANGLE_UTIL_IMPLEMENTATION)
-#            define ANGLE_UTIL_EXPORT __attribute__((visibility("default")))
-#        else
-#            define ANGLE_UTIL_EXPORT
-#        endif
+#        define ANGLE_UTIL_EXPORT __attribute__((visibility("default")))
 #    else
 #        define ANGLE_UTIL_EXPORT
 #    endif