community/chez-scheme: make sure check() fails on test failures
From the upstream BUILDING
file:
NB: A complete run does not imply no errors occurred. To check for errors, look at the file $W/mats/summary […].
To make sure check() fails on test failure, we just compare the summary file against an expected summary file with diff(1). This is also what upstream ChezScheme does for the GitHub CI workflow.