1417931 - Look into removing the PREF_DIR variable from the recursive make backend

Status: NEW

(Firefox Build System :: General, enhancement)

Description

[(not currently active) Ted Mielczarek]

I removed a use of `PREF_DIR` that had been in browser/locales/Makefile.in when migrating the rule to moz.build, because it turns out that in browser, where DIST_SUBDIR is always set, it will always have the same value:
https://searchfox.org/mozilla-central/rev/a662f122c37704456457a526af90db4e3c0fd10e/config/rules.mk#1206

It's used in a handful of other places (ignore the js/jsm/cpp hits, they're unrelated):
https://searchfox.org/mozilla-central/search?q=PREF_DIR&path

The bits in mobile might be tricky, since it doesn't set DIST_SUBDIR that means that the value would vary between normal packaging and langpack packaging. If that actually winds up happening we'd need to fix that somehow.

I don't really understand the usage in the package-manifest.in files. I don't think those are used for anything but application packaging, so the value there should effectively be fixed and we could just replace it with the right string, I think?