ox: Fix async export with native compilation
* lisp/ox-beamer.el (org-beamer-export-to-pdf):
* lisp/ox-icalendar.el (org-icalendar-export-to-ics):
* lisp/ox-koma-letter.el (org-koma-letter-export-to-pdf):
* lisp/ox-man.el (org-man-export-to-pdf):
* lisp/ox-texinfo.el (org-texinfo-export-to-info): Quote lambda.
Quote or name lambdas to prevent their compilation into anonymous
functions which cannot be passed to the external async emacs process.