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

[GHC]

#10726: Upgrade MingW-w64 distributions for windows
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        Reporter:  Phyx-             |                Owner:
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:  7.10.3
       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 Rev(s):  Phab:D1123
  #10435                             |
       Wiki Page:                    |
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Comment (by Phyx-):

 @lukexi thanks, can reproduce it now :)

 @Elieux unfortunately it seems it's not that easy. The `rts` seems to be a
 special case again. The linker seems to ignore the `extra-libraries` from
 the `package.conf`, which explains why you can put anything you want in
 there and it'll still compile.

 {{{
 128 emptyPLS :: DynFlags -> PersistentLinkerState
 129 emptyPLS _ = PersistentLinkerState {
 130                         closure_env = emptyNameEnv,
 131                         itbl_env    = emptyNameEnv,
 132                         pkgs_loaded = init_pkgs,
 133                         bcos_loaded = [],
 134                         objs_loaded = [],
 135                         temp_sos = [] }
 136

 137   -- Packages that don't need loading, because the compiler
 138   -- shares them with the interpreted program.
 139   --
 140   -- The linker's symbol table is populated with RTS symbols using an
 141   -- explicit list.  See rts/Linker.c for details.
 142   where init_pkgs = [rtsUnitId]
 }}}


 > Therefore i believe proper solution should be linking `libmingwex.a`as a
 whole archive when building ghc.exe, instead of just letting GCC to link
 only used symbols as it does by default.

 Hence the temporary solution. The package.conf for the `rts` ignores the
 `extra-libraries` section in the linker. Windows isn't alone here, Mac
 also re-exports some symbols. And before ripping this out I want to know
 why. Also I think it's riskier then just adding some extra symbols. **As**
 it is right now, there is no way to use `libmingwex.a` on Windows.

 > Reexporting those symbols seems like a bad idea, because, if I'm not
 mistaken, RTS gets linked into ever executable produced by GHC, so this
 way we are actually forcing possibly unnecessary symbols into every
 executable?

 Yes, I don't know why it was done this way. However we are already re-
 exporting some of the symbols. Quite a few in fact. Yes the proper
 solution is to rip the symbols out and just link against `libmingwex.a`
 which may get in to `8.0`, but for `7.10.3` I doubt it. It's already at
 `RC3`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10726#comment:47>
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