patch applied (ghc): Only touch the configure stamp if configure succeeds

[Ian Lynagh]

Thu May  3 05:39:13 PDT 2007  Ian Lynagh <igloo at earth.li>
  * Only touch the configure stamp if configure succeeds
  We don't touch $@ if configure failed as we would prefer to try
  configuring it next time round, rather than assuming it'll still fail.
  This is particularly important for corelibs, where failure means the
  build dies!

    M ./libraries/Makefile -13 +17