Added arm64 support for NetBSD

src/threading.cpp

@@ -494,6 +494,8 @@ gb_internal u32 thread_current_id(void) {
 	thread_id = find_thread(NULL);
 #elif defined(GB_SYSTEM_FREEBSD)
 	thread_id = pthread_getthreadid_np();
+#elif defined(GB_SYSTEM_NETBSD)
+	thread_id = (u32)_lwp_self();
 #else
 	#error Unsupported architecture for thread_current_id()
 #endif