LibELF: Implement _invoke_entry for aarch64

Userland/Libraries/LibELF/Arch/aarch64/entry.S

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Nico Weber <thakis@chromium.org>
+ * Copyright (c) 2023, Timon Kruiper <timonkruiper@gmail.com>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -8,5 +9,4 @@
 .hidden _invoke_entry
 .type _invoke_entry,@function
 _invoke_entry: # (argc, argv, envp, entry)
-    # FIXME: Possibly incomplete.
-    ret
+    br x3