[GHC] #12599: Add Hadrian build artifacts to gitignore

[GHC]

#12599: Add Hadrian build artifacts to gitignore
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #8040             |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by bgamari):

 * related:   => #8040


Comment:

 It seems like one of the first things to look at is #8040.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12599#comment:3>
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