[GHC] #10705: make configure warn when ghc-tarballs is missing on windows and provide guidance to download it.

[GHC]

#10705: make configure warn when ghc-tarballs is missing on windows and provide
guidance to download it.
-------------------------------------+-------------------------------------
        Reporter:  Phyx-             |                   Owner:
            Type:  task              |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Build System      |                 Version:  7.11
      Resolution:                    |                Keywords:
Operating System:  FreeBSD           |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:  #9218             |  Differential Revisions:  Phab:D1108
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Comment (by Thomas Miedema <thomasmiedema@…>):

 In [changeset:"a442800fd27952bff9bf9773f514ee062f4b55d0/ghc"
 a442800f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="a442800fd27952bff9bf9773f514ee062f4b55d0"
 Build system: remove function keyword from configure.ac (#10705)

 This fixes the FreeBSD build.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10705#comment:8>
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