Remove a check from strerror_r test.

It's not always true: on Android, strerror_r with invalid errno
prints "Unknown error ..." to the buffer and returns 0.

This test now only checks that strerror_r does not crash.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@201321 91177308-0d34-0410-b5e6-96231b3b80d8