* Simplify CI workflow * CI: upgrade Ubuntu's Clang version to 12 * CI: upgrade macOS runner to version 11 (Big Sur) * CI: temporarily disable the M1 runner * CI: output test suite log upon failure * CI: avoid brew update/upgrade steps Since it may take a long time. * CI: all jobs are supposed to succeed * Fix test_descriptors.c failure after f8c2a36 Use a RANDOM image to create many crops from one source.