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

[GHC]

#8683: add "cpp program" and "cpp program options" to settings file
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        Reporter:  carter            |            Owner:
            Type:  feature request   |           Status:  patch
        Priority:  normal            |        Milestone:  7.8.1
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:  #8439
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Comment (by carter):

 so as a way of "fuzzing" this patch, i'm trying out doing stuff like

 ./configure --with-gcc=clang --with-cpp=gcc
 and ./configure --with-gcc=gcc --with-cpp=cpphs
 and ./configure --with-gcc=gcc --with-cpp=clang

 (which is perhaps a bit daft, but seems to be a good way to understand
 what i'm not doing right for the build system :) )

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8683#comment:14>
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