Use clang-cl to link the DLL tests

git-svn-id: http://address-sanitizer.googlecode.com/svn/trunk@1867 3c3640eb-14a6-2bb8-0b94-e9e73afe33f5
Drop the EXTRA_GUEST_LIBS var, not needed anymore

git-svn-id: http://address-sanitizer.googlecode.com/svn/trunk@1868 3c3640eb-14a6-2bb8-0b94-e9e73afe33f5