[GHC] #16120: Hadrian should use cabal build-tools installed Alex and Happy if necessary

[GHC]

#16120: Hadrian should use cabal build-tools installed Alex and Happy if necessary
-------------------------------------+-------------------------------------
        Reporter:  adamse            |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Build System      |              Version:  8.6.3
  (Hadrian)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by adamse):

 hvr suggests using

 {{{
 $ cabal new-exec --project=$PWD/hadrian/cabal.project sh -- -c 'command -v
 alex'
 /home/hvr/.cabal/store/ghc-8.4.4/alex-3.2.4-4006f020d0bf93fca9fc50e9f961c4a2af3341f7a44d2bfa6f7feb9c7d6e930b/bin/alex
 }}}

 or

 {{{
 $ cabal new-exec --project=$PWD/hadrian/cabal.project which -- alex
 /home/hvr/.cabal/store/ghc-8.4.4/alex-3.2.4-4006f020d0bf93fca9fc50e9f961c4a2af3341f7a44d2bfa6f7feb9c7d6e930b/bin/alex
 }}}

 To find the build-tools.

 Is it possible for hadrian to call cabal in this way?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16120#comment:1>
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