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

[GHC]

#10726: Upgrade MingW-w64 distributions for windows
-------------------------------------+-------------------------------------
        Reporter:  Phyx-             |                   Owner:  Phyx-
            Type:  task              |                  Status:  patch
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Build System      |                 Version:  7.11
      Resolution:                    |                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                             |
-------------------------------------+-------------------------------------

Comment (by awson):

 Could we, perhaps, use Msys2 builds for this? They are of a high quality
 and pretty well supported. Also they have gcc-5.2 and, most important,
 recently released binutils-2.25.1 which have a very important bug (wrong
 linking of 64-bit import libraries generated by MS linker) fixed.

 As of today the transitive closure of packages required is (I believe)
 this:
 {{{
 mingw-w64-x86_64-crt-git-5.0.0.4531.49c7046-1
 mingw-w64-x86_64-winpthreads-git-5.0.0.4538.78dca70-1
 mingw-w64-x86_64-headers-git-5.0.0.4531.49c7046-1
 mingw-w64-x86_64-libwinpthread-git-5.0.0.4538.78dca70-1
 mingw-w64-x86_64-zlib-1.2.8-8
 mingw-w64-x86_64-isl-0.14.1-2
 mingw-w64-x86_64-mpc-1.0.3-2
 mingw-w64-x86_64-mpfr-3.1.3.p0-2
 mingw-w64-x86_64-gmp-6.0.0-3
 mingw-w64-x86_64-gcc-libs-5.2.0-3
 mingw-w64-x86_64-binutils-2.25.1-1
 mingw-w64-x86_64-libiconv-1.14-5
 mingw-w64-x86_64-gcc-5.2.0-3
 }}}

 The new repo of Msys2 packages is http://repo.msys2.org/mingw.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10726#comment:3>
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