[GHC] #910: --make should have a -j flag for parallel building

[GHC]

#910: --make should have a -j flag for parallel building
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        Reporter:  igloo             |                Owner:
            Type:  feature request   |               Status:  closed
        Priority:  normal            |            Milestone:  ⊥
       Component:  Compiler          |              Version:  6.4.2
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:  N/A
      Blocked By:  8184, 8235        |             Blocking:
 Related Tickets:  #9221             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by rrnewton):

 For me, typical stack builds spend a huge amount of time bottlenecked on
 just one or two ghc compiles.  Yes, we could push towards stack and other
 tools dynamically provisioning cores to GHC instances.  But, in the short
 term GHC doesn't actually get decent parallel scaling anyway (#9221) so I
 really just want `-j2` or `-j3`.  And that limited level of
 oversubscription I'm not very worried about (the overall builds spend so
 little their time with decent parallel utilization anyway).

 Do we have a policy for priorities of env vars versus flags in general?  I
 think command line flags should take precedence.  Then any smart tools
 that know how to manage "ghc -j" can override any system wide default.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/910#comment:65>
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