[m-rev.] for post-commit review: fix mmc_make test case failures

[Zoltan Somogyi]

For review by anyone.

BTW, I could not verify in which grades these test cases used to fail,
because the web server on testing.mercurylang.org is unresponsive.
(A ping does get returned, so the OS is alive.) Does anyone know
what is causing that?

Zoltan.
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