bug#46256: [feature/native-comp] AOT eln files ignored if run from build tree

[Eli Zaretskii]

Also, while compiling I see this warning:

  comp.c: In function 'eln_load_path_final_clean_up':
  comp.c:4514:15: warning: trampoline generated for nested function 
'return_nil' [-Wtrampolines]
   4514 |   Lisp_Object return_nil (Lisp_Object arg) { return Qnil; }
        |               ^~~~~~~~~~

Why do we need this nested function on Windows, and what is the story
about the trampoline?  And how to avoid the warning?

Thanks.