Configure cpp in ghc settings rather than hardcode

Currently, we're configuring the haskell preprocessor and haskell preprocessor flags into the ghc settings file, and ghc uses that configuration to invoke that program.

Unlike the haskell preprocessor, the c preprocessor, used to preprocess Cmm files, is hardcoded in GHC.SysTools.Cpp as cc -E.

For the sake of uniformity, we should also configure the C preprocessor into settings, and have GHC trust and use that configuration.

CC @bgamari

Edited May 20, 2023 by Rodrigo Mesquita

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