Right now these variables are partially in moz.build and partially in Makefile.in. This ticket tracks making them moz.build Path instances.

Bug 1200876 - Work in progress on using Path() in extra_jars. r=nalexander blassey sees issues with absolute paths in backend.mk files building on Windows. ted suggests that mozmake expects "Windows native paths", like 'c:/foo/bar', where-as the existing build backends produce "msys paths", like /c/foo/bar. This was a stab at using AbsolutePath() to address this, but AbsolutePath() doesn't currently do the right thing either. Posting this just to show where some of the work would happen and capture the experiment.

Instead, I removed the relevant moz.build pieces in https://bugzilla.mozilla.org/show_bug.cgi?id=1255924 and its precursors.