CDS custom loader supported was limited to a few platforms because we didn't have time to test for all platforms.

Now that this feature is quite stable, we should support all platforms.

https://github.com/openjdk/jdk/blob/034788a02cbe1f80fc1581ec307a3d54bef380b4/src/hotspot/share/cds/classListParser.cpp#L440

InstanceKlass* ClassListParser::load_class_from_source(Symbol* class_name, TRAPS) {
#if !(defined(_LP64) && (defined(LINUX) || defined(__APPLE__)))
  // The only supported platforms are: (1) Linux/64-bit and (2) Solaris/64-bit and
  // (3) MacOSX/64-bit
  // This #if condition should be in sync with the areCustomLoadersSupportedForCDS
  // method in test/lib/jdk/test/lib/Platform.java.
  error("AppCDS custom class loaders not supported on this platform");
#endif