This should be 0 rebuilds, except it fixes the installer tests, as
lib.filesets is somehow broken when combining chroot stores with
channel references (???).
Running nixosTests.installer.simple with this reverted will reproduce
the issue consistently.
CC @infinisil
This allows us to reuse our existing infrastructure which alreday
contains workarounds for various issues. Prior to this,
ghc-settings-edit wouldn't compile with musl for some
reason.