Spurious failures on unsupported systems

[shlevy]

If I touch a package that is known not to build on darwin, I get an error like NixOS/nixpkgs#35666 (comment)

[7c6f434c]

Timeouts could also benefit from being reported separately. Unlike platform checks, timeout failures can sometimes require fetching the whole log (if more than ten packages depend on the long-build one)

[7c6f434c]

I am not sure how feasible it is to recognise out-of-space failures separately…