Prefer 'env not' over 'not env' in tests.

That way, lit's builtin 'env' command can be used for the 'env' bit.

Also it's clearer that way that the 'not' shouldn't cover 'env'
failures.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@374749 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed