Release lock before finalizing sound samples (#8468)

Source/engine/sound.cpp

@@ -192,10 +192,17 @@ const auto OptionChangeDevice = (GetOptions().Audio.device.SetValueChangedCallba
 } // namespace
 
 void ClearDuplicateSounds()
+{
+	// Move sound samples to a temporary list,
+	// avoiding a deadlock that involves SDL's
+	// mixer lock being taken by finalizers
+	std::list<std::unique_ptr<SoundSample>> drain;
 	{
 		const std::lock_guard<SdlMutex> lock(*duplicateSoundsMutex);
+		drain = std::move(duplicateSounds);
 		duplicateSounds.clear();
 	}
+}
 
 void snd_play_snd(TSnd *pSnd, int lVolume, int lPan, int userVolume)
 {