This reverts commit a85b07cbcb as
executing the tests in parallel makes them flaky. This can be seen very
easily on armv7l machines (and probably other machines that are slower
than common x86_64 machines as well), but is also reproducible on
x86_64.
This fixes#91706.
Currently the tests take an eternity and are also sometimes flaky. By
following upstream in using xdist for parallel test execution we at
least get the feedback cycle down. On my machine that means instead of
running this for ~25min it runs in 1 minute and 10 seconds.
Since 2.9 bash-completion hardcodes paths in pkgconfig file. We want to
be able to override certain paths, so this commit restores the original
behaviour.
https://github.com/NixOS/nixpkgs/issues/71662