testsuite: Disable linkwhole test on Windows
testsuite: Disable linkwhole test on Windows

It relies on System.Posix.DynamicLinker, which is not available.

ezyang/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc