Add REQUIRES to tests that fail when an x86 backend is not present.
There was a recent review D47748 to add REQUIRES x86 to all the tests that needed X86. Since that landed there have been a few new tests added without REQUIRES. We are going to remove the X86 backend from one of the linaro buildbots to speed it up and can keep the LLD tests up to date. The tests were identified by a run of the buildbot.
FAIL: lld::guardcf-align.s FAIL: lld::icf16.s FAIL: lld::icf13.s FAIL: lld::icf15.s FAIL: lld::icf17.s FAIL: lld::libcall-archive.ll