Remove test coverage added in 221067 due to it being non-portable.

Will try to find a portable way to test this (or a fixed-target test I
can add such coverage to) shortly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221068 91177308-0d34-0410-b5e6-96231b3b80d8