[lld-macho] Disable some tests that are failing on Windows

lto-object-path.ll, like stabs.s, is disabled on Windows as the path
separators make it difficult to write a test that works across
platforms.

This diff also disables implicit-dylibs.s on Windows as we seem to emit
LC_LOAD_DYLIBs in a different order on that platform. This seems like a
bug in LLD that needs to be addressed (in a future diff).