[GHC] #12487: configure.ac uses wrong triple information.

[GHC]

#12487: configure.ac uses wrong triple information.
-------------------------------------+-------------------------------------
        Reporter:  Phyx-             |                Owner:  Phyx-
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Build System      |              Version:  8.0.1
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Building GHC      |  Unknown/Multiple
  failed                             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D2452
       Wiki Page:                    |
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Comment (by Sergei Trofimovich <siarheit@…>):

 In [changeset:"0cc3931bd7831fa8d042f968a5a9114534a656e4/ghc"
 0cc3931b/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="0cc3931bd7831fa8d042f968a5a9114534a656e4"
 configure.ac: fix --host= handling

 The following command fails as:
     $ ./configure --prefix=/usr \
         --build=x86_64-pc-linux-gnu \
         --host=x86_64-pc-linux-gnu \
         --target=x86_64-pc-linux-gnu
     configure: error:
     You've selected:

       BUILD:  x86_64-unknown-linux
       HOST:   x86_64-unknown-linux
       TARGET: x86_64-unknown-linux

     BUILD must equal HOST;

 18f06878ed5d8cb0cf366a876f2bfea29647e5f0 changed native
 configure $build/$host/$target checks to ghc-mangled ones,
 but not completely.

 Signed-off-by: Sergei Trofimovich <siarheit at google.com>

 Reviewers: rwbarton, erikd, austin, hvr, bgamari, Phyx

 Reviewed By: Phyx

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2508

 GHC Trac Issues: #12487
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12487#comment:5>
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