I discovered some of these tests had cmp statements that weren't
actually being run. I had also recently copied this broken setup for a
new test around chained fixups. Fixing this revealed that the binaries
did differ because of their code signature so I regenerated the fixture
here with this source:
c int main() { return 0; }
Passing -Wl,-no_adhoc_codesign on my M1 machine to make sure it didn't
get any signature.