Tests: Allow RunCMake.MaxRecursionDepth to test public-facing default limit

Previously we compiled in a smaller default limit during nightly testing
and CI builds, so we were not testing the same default limit that
end-users will see.  Instead, set the limit during testing using an
environment variable so that we can unset it when testing the default
limit in `RunCMake.MaxRecursionDepth`.
2 files changed