[GHC] #10728: Add e.g. "-N<=4" in addition to the fixed "-N4" and variable "-N" RTS options

[GHC]

#10728: Add e.g. "-N<=4" in addition to the fixed "-N4" and variable "-N" RTS
options
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        Reporter:  rrnewton          |                   Owner:  simonmar
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Runtime System    |                 Version:  7.10.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #9221, #8224      |  Differential Revisions:
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Comment (by simonmar):

 Yes, I think this would be good.  I've actually used `setNumCapabilities`
 and `getNumProcessors` to do this as @rrnewton suggests, but having a flag
 would be easier.  Any takers?  It's not hard.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10728#comment:4>
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