[GHC] #5874: Document autoconf dependency in README

[GHC]

#5874: Document autoconf dependency in README
------------------------------+---------------------------------------------
 Reporter:  JamesFisher       |          Owner:                  
     Type:  bug               |         Status:  new             
 Priority:  normal            |      Component:  Build System    
  Version:  7.4.1             |       Keywords:                  
       Os:  Unknown/Multiple  |   Architecture:  Unknown/Multiple
  Failure:  None/Unknown      |       Testcase:                  
Blockedby:                    |       Blocking:                  
  Related:                    |  
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 The {{{boot}}} script calls {{{autoreconf}}} on line 204.  If not present
 this gives the error message

 {{{
 [...]
 Booting .
 Can't exec "autoreconf": No such file or directory at boot line 204,
 <PKGS> line 2.
 Running autoreconf failed with exitcode -1 at boot line 204, <PKGS> line
 2.
 }}}

 For those following the {{{README}}} to build GHC for the first time this
 is unfriendly.  I had to Google to find that I had to install the
 {{{autoconf}}} package (on Ubuntu).

 The dependency on {{{autoconf}}} should be documented in {{{README}}}.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5874>
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