If you doing it locally only, I don't see the difference from make that will just keep your old .o files.
If you using it distributed between different developer, how do you make sure the cache result is secure? A shared cache where everyone can contribute to is really hard (impossible?) to make secure. Someone could add malicious code the cache that then everyone will use.
If you using it distributed between different developer, how do you make sure the cache result is secure? A shared cache where everyone can contribute to is really hard (impossible?) to make secure. Someone could add malicious code the cache that then everyone will use.