There is the `-C` option of course. It's supposedly good for the standard tests that waste all the time, but not so much for the ad-hoc tests various projects use, which have an unfortunate chance of being buggy or varying across time.

... I wonder if it's possible to manually seed a cache file with only known-safe test results and let it still perform the unsafe tests? Be sure to copy the cache file to a temporary name ...

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I've thought about rewriting `./configure` in C (I did it in Python once but Python's portability turned out to be poor - Python2 was bug-free but killed; Python3 was unfixably buggy for a decade or so). Still have a stub shell script that reads HOSTCC etc. then quickly builds and executes `./configure.bin`.