#3996 Very long compilation times for asconhash tests with --nolabelopt

[Philipp Klaus Krause]

When using --nolabelopt, I see very long compilation times for the asconhash256_impl_opt8 and asconhash256_impl_opt8_lowsize tests (several hours on a Ryzen AI Max+ 395) for multiple targets, e.g.:

--max-allocs-per-node 8192 --noloopreverse --nolabelopt --nostdinc -mf8l
--max-allocs-per-node 8192 --nolabelopt --opt-code-size --nostdinc -ms08
--max-allocs-per-node 128 --nolabelopt --nolospre --opt-code-size --nostdinc -mds390

This issue was found in the fuzzing branch; I'll disable the asconhash tests for fuzzing for now.