Revert "[lld-macho] No need to explicitly specify -arch in tests"

This reverts commit 51c5baac and also
337fb8c7 - "[lld-macho] Set REQUIRES:
x86 on more tests".

These patches cause test crashes:

http://lab.llvm.org:8011/builders/ppc64le-lld-multistage-test/builds/10054