This ensures patches and Hackage revisions are applied to the base
tarball which may be necessary in order for the packages to build in the
shell environment.

In #296645, envFunc (and thus shellFor) was changed from
`mkDerivation {phases=[..]}` to `runCommand ..`. So since
then, the derivation of shellFor contains a `buildCommand`
("echo $nativeBuildInputs $buildInputs > $out"),
and as a result the custom phases defined in shellFor's
test were ignored.

After final improvements to the official formatter implementation,
this commit now performs the first treewide reformat of Nix files using it.
This is part of the implementation of RFC 166.

Only "inactive" files are reformatted, meaning only files that
aren't being touched by any PR with activity in the past 2 months.
This is to avoid conflicts for PRs that might soon be merged.
Later we can do a full treewide reformat to get the rest,
which should not cause as many conflicts.

A CI check has already been running for some time to ensure that new and
already-formatted files are formatted, so the files being reformatted here
should also stay formatted.

This commit was automatically created and can be verified using

    nix-build https://github.com/infinisil/treewide-nixpkgs-reformat-script/archive/a08b3a4d199c6124ac5b36a889d9099b4383463f.tar.gz \
      --argstr baseRev 78e9caf153f5a339bf1d4c000ff6f0a503a369c8
    result/bin/apply-formatting $NIXPKGS_PATH

The current version of linear (1.22) has incorrect constraints in its
cabal file (which has been corrected in a revision), so it is causing
this test to fail.

This commit just switches to another arbitrary package (cereal) for the
tests.

This commit does the following two things:

1.  Changes the Haskell package used in the extraDependencies test from
    releaser to conduit.  The reason for this is that conduit is more
    of a "core" package in Haskell, and it is more likely to always be
    working.  (If conduit is not compiling, then large chunks of Hackage
    won't be working.)

2.  Tighten up the GHCi test to actually use the package from
    extraDependencies.  It appears that GHCi can fail to import the
    package from extraDependencies, and that doesn't cause GHCi to
    return an error code, which means the test isn't actually testing
    anything.

    This new change makes it so that if the package from
    extraDependencies is actually not included for some reason, then
    this shellFor test should fail.

An example use case is when you have Haskell scripts that use
libraries that don't occur in your packages' dependencies.

This allows packagePlatforms to pick up on the overall supported
platforms and schedule builds on Hydra for more than the evaluation
platform (usually x86_64-linux).

Contrary to database-id-class, linear is part of stackage and actively
maintained, so the test is less likely to fail due to version
constraint issues as it is currently.