Try to be compatible with POSIX shell

The == operator doesn't exist in POSIX's test. We aren't using globs
anyway, so simplify some uses of this to = (for strings) or -eq (for
numbers)

git-svn-id: https://llvm.org/svn/llvm-project/test-suite/trunk@211729 91177308-0d34-0410-b5e6-96231b3b80d8