[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:                    |
-------------------------------------+-------------------------------------

Comment (by adamse):

 This change is enough for the configure script to find alex & happy. I do
 not know if stack has support for installing build tools, so I cannot
 comment on that part.

 Gitlab MR: https://gitlab.haskell.org/ghc/ghc/merge_requests/69

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16120#comment:10>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler