[GHC] #10726: Upgrade MingW-w64 distributions for windows

[GHC]

#10726: Upgrade MingW-w64 distributions for windows
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        Reporter:  Phyx-             |                   Owner:  Phyx-
            Type:  task              |                  Status:  merge
        Priority:  normal            |               Milestone:  7.10.3
       Component:  Build System      |                 Version:  7.11
      Resolution:  fixed             |                Keywords:
Operating System:  Windows           |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #9218 #9014       |  Differential Revisions:  Phab:D1123
  #10435                             |
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Comment (by tejon):

 Just found this via @hanjoosten in a MinGHC issue thread. Haven't tested
 yet, but there's a very good chance this will fix building the GTK+
 bindings on Windows: current failures mostly revolve around attempts to
 use -pthreads, which is not available in GCC 4.6.3 but is as of 4.9.x.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10726#comment:21>
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