patch applied (packages/Cabal): Only use ld -x on systems where ld supports that.

[Ian Lynagh]

Tue Oct 23 11:37:38 PDT 2007  Duncan Coutts <duncan at haskell.org>
  * Only use ld -x on systems where ld supports that.
  Hopefully this fixes it for both ordinary builds and via ghc makefiles.

    M ./Distribution/Simple/GHC.hs -5 +25
    M ./Distribution/Simple/GHC/Makefile.in -1 +1