Cleanup XDG_CACHE_HOME which affects caching of pocl/loopy/sumpy

[isuruf]

See

sumpy/test/test_distributed.py

Lines 38 to 39 in 4ad3d28

	# FIXME: should clean up this directory after running the tests
	os.environ["XDG_CACHE_HOME"] = os.path.join(cache_dir, str(mpirank))

I'm guessing that's one of the reasons for increased CI timing.

Btw, what are the conflicts that this is supposed to solve?

[inducer]

Summoning @gaohao95. Added here: https://github.com/inducer/sumpy/pull/137/files#diff-6ca98cf32babcf9b01b2623785a858f1f4fabeaf81e2ee6b53666ded38fad7faR33

[gaohao95]

Btw, what are the conflicts that this is supposed to solve?

Usually on a cluster all MPI ranks share the same file system. If ranks use the same location for cache, file locking could serialize all ranks.

I don't think this matters for test cases so we can probably remove that if it's a hurdle.

[inducer]

increased CI timing

You sure it's not just the added distributed tests? How big of an increase do you see?