warnings thrown on native-comp

[titaniumbones]

Hi, thanks for this awesome tool!

I am running the pgtk branch with native comp enabled, emacs 28.0.50-git, very recent (upgraded today). On compilation, I get these warnings; I have also had a lot of trouble using use-package with this package i nthe last few weeks, which may (or may not!) be related to these warnings:

Warning (comp): org-pdftools.el:46:1: Warning: custom-declare-variable `org-pdftools-get-desc-function' docstring wider than 80 characters Disable showing Disable logging
Warning (comp): org-pdftools.el:55:1: Warning: custom-declare-variable `org-pdftools-path-generator' docstring wider than 80 characters Disable showing Disable logging
Warning (comp): org-pdftools.el:78:1: Warning: custom-declare-variable `org-pdftools-export-style' docstring wider than 80 characters Disable showing Disable logging
Warning (comp): org-pdftools.el:121:1: Warning: attempt to let-bind constant ‘t’ Disable showing Disable logging
Warning (comp): org-pdftools.el:121:1: Warning: attempt to let-bind constant ‘t’ Disable showing Disable logging
Warning (comp): org-pdftools.el:392:28: Warning: assignment to free variable ‘org-pdftools-prefix’ Disable showing Disable logging
Warning (comp): org-pdftools.el:392:4: Warning: reference to free variable ‘org-pdftools-prefix’ Disable showing Disable logging
Warning (comp): org-pdftools.el:371:17: Warning: the function ‘org-export-file-uri’ is not known to be defined. Disable showing Disable logging

I know very little about hte constraints that compilation imposes, but putting this here as a reference point, since native-comp has been merged to master & will likely become more commonly used soon.