Estimated hours taken: 0.5
Fix a problem where the test cases were sometimes failing
if old /tmp/mmake* directories were left lying around.
scripts/ml.in:
scripts/mmake.in:
When creating the temporary directory, if mkdir fails (e.g.
because that directory already exists), then try again with a
different directory name. Only report an error if it fails 20
times in a row.
98e67d2201