[BUG] Async pdf export broken with native-comp

[Sébastien Miquel]

Hi,

The async pdf export functionality appears to be broken with latest org 
and a
recent emacs version compiled with native-comp enabled (I have not tested
without native-comp).

To reproduce:

 - use `emacs -q` and an empty init.el file (your init file gets picked 
up by
   the async emacs instance)
 - (setq org-export-async-debug t)
 - find any org file and hit =C-c C-e C-a C-l C-p= to export as pdf file.

The async process will exit abnormaly.

The issue stems from this line in `org-export-to-file`
 :       (ignore-errors (funcall ',post-process ,file))

In `org-latex-export-to-pdf`, this `post-process` is set to
 :       (lambda (file) (org-latex-compile file))

I think native-comp compiles this lambda, which messes things up.

As a fix, you can quote the lambda in `org-latex-export-to-pdf`
 :       '(lambda (file) (org-latex-compile file))

The same applies to other backends but I don't know if it's the right 
thing to do.

Regards,

--
Sébastien Miquel