utopia-riseGH-842 Fix thread context classloader (utopia-rise#848)

Author: chippmann

kt/godot-library/godot-core-library/src/main/kotlin/godot/runtime/Bootstrap.kt

@@ -33,7 +33,6 @@ internal class Bootstrap {
  }
 
  fun finish() {
- Thread.currentThread().contextClassLoader = null
  clearClassesCache()
  serviceLoader.reload()
  }

src/gd_kotlin.cpp

@@ -251,6 +251,8 @@ bool GDKotlin::load_bootstrap() {
 
  JVM_LOG_VERBOSE("Loading bootstrap jar: %s", bootstrap_jar);
  bootstrap_class_loader = ClassLoader::create_instance(env, bootstrap_jar, jni::JObject(nullptr));
+
+ // set context classloader to bootstrap initially
  bootstrap_class_loader->set_as_context_loader(env);
  }
 
@@ -318,6 +320,9 @@ bool GDKotlin::load_user_code() {
  bootstrap_class_loader->get_wrapped()
  );
 
+ // update context classloader to use usercode jar
+ user_class_loader->set_as_context_loader(env);
+
  bootstrap->init_jar(env, user_class_loader->get_wrapped());
  delete user_class_loader;
  return FileAccess::exists(user_code_path);
@@ -326,6 +331,10 @@ bool GDKotlin::load_user_code() {
 
 void GDKotlin::unload_user_code() {
  jni::Env env {jni::Jvm::current_env()};
+
+ // reset context classloader to bootstrap
+ bootstrap_class_loader->set_as_context_loader(env);
+
  bootstrap->finish(env);
  TypeManager::get_instance().clear();
  jar.unref();