build: avoid pylint randomness
build: avoid pylint randomness

-j seems to introduce non-determinism:
https://github.com/PyCQA/pylint/issues/4356

With -j4, we'd have occasional (1 in 20?) failures on CI.

hugovk/coveragepy,nedbat/coveragepy,hugovk/coveragepy,hugovk/coveragepy,nedbat/coveragepy,hugovk/coveragepy,nedbat/coveragepy,hugovk/coveragepy,nedbat/coveragepy,nedbat/coveragepy