Automatically generated path that adds flag `REQUIRES_UNIFIED_BUILD = True` to `moz.build`
when the module governed by the build config file is not buildable outside on the unified environment.
This needs to be done in order to have a hybrid build system that adds the possibility of combing
unified build components with ones that are built outside of the unified eco system.
Differential Revision: https://phabricator.services.mozilla.com/D122345
The current code is somewhat non-obvious to a first-time reader, and
OS_TEST is a bizarre thing anyway, since it's actually the name of the
CPU we're running on. We'd do well to minimize the use of OS_TEST.
Note that the complete nuking of the xptcall/md/unix/moz.build lines are
because we don't support OS X/x86 anymore.