[GHC] #8713: Avoid libraries if unneeded (librt, libdl, libpthread)

[GHC]

#8713: Avoid libraries if unneeded (librt, libdl, libpthread)
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              Reporter:  ip1981      |            Owner:
                  Type:  bug         |           Status:  upstream
              Priority:  normal      |        Milestone:
             Component:  GHCi        |          Version:  7.6.3
            Resolution:              |         Keywords:
      Operating System:  Other       |     Architecture:  x86_64 (amd64)
       Type of failure:  GHCi crash  |       Difficulty:  Moderate (less
             Test Case:              |  than a day)
              Blocking:              |       Blocked By:
Differential Revisions:              |  Related Tickets:
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Comment (by ip1981):

 Patch for GHC:
 https://github.com/ip1981/ghc/commit/836b7623ca70231fafc49838adc2f884c9e662c8
 (also attached)

 Patch for unix module: https://github.com/haskell/unix/pull/8

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8713#comment:14>
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