[GHC] #7700: iOS patch no 3: enable/disable terminfo more precisely by os

[GHC]

#7700: iOS patch no 3: enable/disable terminfo more precisely by os
------------------------------+---------------------------------------------
Reporter:  StephenBlackheath  |          Owner:                  
    Type:  bug                |         Status:  new             
Priority:  normal             |      Component:  Compiler        
 Version:  7.7                |       Keywords:                  
      Os:  Unknown/Multiple   |   Architecture:  Unknown/Multiple
 Failure:  None/Unknown       |      Blockedby:                  
Blocking:                     |        Related:                  
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 When cross compiling to iOS, HostOS = darwin and TargetOS = ios. darwin
 has termios but ios doesn't. So we need termios built in stage 0 but not
 stage 1, but the makefiles don't currently allow for that.

 This patch makes it so termios is selected by the right OS for the right
 stage. I've refactored how Windows is handled here, so e.g. the termios
 selection should work correctly for both native windows and a Linux ->
 mingw32 cross compile (though I haven't tested it). Linux -> Windows
 mirrors darwin -> ios, in that it's termios -> no termios.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7700>
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