[O] latex exporting to different directory with v9.0

[Alex Fenton]

Firstly, congratulations and thanks to all the contributors to the new 
release.

One thing that has unfortunately stopped working is my setup for 
exporting to pdf, putting all the intermediary  (.tex, .aux, .bbl, etc) 
and output files in a different directory to the source .org files. My 
setup is basically

project/
- images/
- out/

with all the .org files in the project base directory. A simple 
publishing set-up exported .tex to out/ then called org-latex-compile.

With 9.0, org-latex-compile hands off to org-compile-file, in which (as 
documented) "`default-directory' is set to SOURCE directory during the whole
process." This means, however, that all the image and bibliograpy links 
in the .org files are now broken, since they point to ./img/foo.png and 
not ../img/foo.png

It is easy enough to continue to compile from the base directory with 
latexmk and --output-directory, but how is it now intended to do this 
within org's export/publishing framework?

symlinks are not an option since I'm sometimes working on Windows.

thanks
alex