This should be handled appropriately by a wrapper script around the compiler,
if one wants to insist on the specific linker to be used.  Otherwise this
breaks if the used compiler fails to understand this directive.

I believe that using a specific linker should be part of the compilers
toolchain, we delegate to and not hardcoded here in ghc.

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

Reviewed By: bgamari

Subscribers: snowleopard, davean, dfeuer, thomie, erikd

Differential Revision: https://phabricator.haskell.org/D3351