[GHC] #8683: add "cpp program" and "cpp program options" to settings file

[GHC]

#8683: add "cpp program" and "cpp program options" to settings file
-------------------------------------+------------------------------------
        Reporter:  carter            |            Owner:  carter
            Type:  feature request   |           Status:  patch
        Priority:  high              |        Milestone:  7.8.3
       Component:  Compiler          |          Version:  7.8.1-rc2
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:  9094              |  Related Tickets:  #8439
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Comment (by dagit):

 Mixing `clang` and `gcc` in the same build may lead to weird issues in
 some cases. I don't think it will be common, but it's something to watch
 out for.

 Imagine this scenario: You're making an FFI binding and `clang` and `gcc`
 use different definitions in their respective libraries. Or stranger yet,
 someone has written their library to behave differently depending on
 whether it's compiled with `clang` or `gcc` (let's hope no one does that).

 Thinking about this lead to realizing that cabal + hsc2hs exhibits a
 related problem: https://github.com/haskell/cabal/issues/1858

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8683#comment:62>
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