Fix thread IDs.

On Linux, thread IDs were not properly assigned with the current approach.
The line:
`std::thread new_thread(&Thread::callback, _thread_id_hash(thread.get_id()), p_settings, p_callback, p_user);`
does not work because the thread ID is not assigned until the thread starts.

This PR changes the behavior to use manually generated thread IDs. Additionally, if a thread is (or may have been created) outside Godot, the method `Thread::attach_external_thread` was added.

2 files changed, 4 insertions, 2 deletions

diff --git a/platform/android/export/export_plugin.cpp b/platform/android/export/export_plugin.cpp
index 0f0132a5d1..f52edf2b61 100644
--- a/platform/android/export/export_plugin.cpp
+++ b/platform/android/export/export_plugin.cpp
@@ -3306,6 +3306,8 @@ EditorExportPlatformAndroid::EditorExportPlatformAndroid() {
 EditorExportPlatformAndroid::~EditorExportPlatformAndroid() {
 #ifndef ANDROID_ENABLED
 	quit_request.set();
-	check_for_changes_thread.wait_to_finish();
+	if (check_for_changes_thread.is_started()) {
+		check_for_changes_thread.wait_to_finish();
+	}
 #endif
 }
diff --git a/platform/android/java_godot_lib_jni.cpp b/platform/android/java_godot_lib_jni.cpp
index 1a0087e18d..f32617e674 100644
--- a/platform/android/java_godot_lib_jni.cpp
+++ b/platform/android/java_godot_lib_jni.cpp
@@ -244,7 +244,7 @@ JNIEXPORT jboolean JNICALL Java_org_godotengine_godot_GodotLib_step(JNIEnv *env,
 	if (step.get() == 0) {
 		// Since Godot is initialized on the UI thread, main_thread_id was set to that thread's id,
 		// but for Godot purposes, the main thread is the one running the game loop
-		Main::setup2(Thread::get_caller_id());
+		Main::setup2();
 		input_handler = new AndroidInputHandler();
 		step.increment();
 		return true;