AppCDS custom loader support on Mac OS X

AppCDS support for custom loaders needs to work on Mac OS X
We need to add Mac X to our AppCDS test matrix.

Since our focus is application developers and we want them
to be able to move seamlessly between their development platforms
of choice and our Cloud.

As of JDK 10, OSX is not on the supported list. This was done due to lack of testing resources, but we should try to support OSX in JDK 11. See http://hg.openjdk.java.net/jdk/jdk10/file/7fc3d62481ba/test/lib/jdk/test/lib/Platform.java#l295

    /*
     * This should match the #if condition in ClassListParser::load_class_from_source().
     */
    public static boolean areCustomLoadersSupportedForCDS() {
        boolean isLinux = Platform.isLinux();
        boolean is64 = Platform.is64bit();
        boolean isSolaris = Platform.isSolaris();
        boolean isAix = Platform.isAix();

        return (is64 && (isLinux || isSolaris || isAix));
    }