Hey all

I help package things for conda-forge, and pillow 8.4 recently got stuck in limbo due to #5624 breaking the build we (need to) use there. We rely on the fact that we can control the MacOS SDK being used (which is explicitly set up by conda-build), but after #5624, the sdk from the system gets preference and ends up breaking (mismatched compiler vs. lib).

I reverted it to get conda-forge/pillow-feedstock#101 out the door, but carrying patches indefinitely is not great.

I haven't studied #5622, but I hope we can find a solution that suits everyone. This could (for example) work with an environment variable that gets precedence if non-empty (but many other solutions would likely be possible).