Add lib32/lib64 to link search path.

Add the lib32/lib64 build directories to the link search path so that
testsuite programs are linked against the newly built runtime.

git-svn-id: svn+ssh://svn.code.sf.net/p/mingw-w64/code/trunk@2782 4407c894-4637-0410-b4f5-ada5f102cad1