Manually expand out the few places where we had a `not ...` substitution
where the substituted value was invoking `env` to alter the environment.
This pattern is not portable and causes problems when using the
integrated shell, such as on Windows. This was identified during the
LLVM update.
This additionally corrects the use of `not` to indicate that it is
expecting a crashing failure. This was resulting in the Windows tests
failing as `not` was not expecting a crashing failure.
