Run Ormolu on GHC (in particular its testsuite)

[amesgen]

GHC and its testsuite contains a lot of Haskell source code with many special cases, so trying to format it with Ormolu can be useful to further increase the robustness of Ormolu.

In amesgen/ormolize-ghc, I added preliminary support for Ormelizing ghc (it is not clear if we ever want to merge this, but it is useful for get a nice log of an Ormolu run on the CPP-clean GHC codebase via nix-build -A hackage.ghc). As many files in the testsuite are supposed to fail when being parsed/compiled, I added a basic whitelist (via an ugly regex) for files I think should be fine. Some extra files have to be excluded as cpphs can't process them.

I uploaded the (slightly cleaned up) log file here: https://gist.github.com/amesgen/6d6d3de90d33b076d1cdf3806aa2c9dd

I will now open some bugs found this way (probably not exhaustive at all).

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Credits for this idea go to @utdemir