Special exit codes for build failure

1xx status codes are used when requested builds failed. The following codes are in use:

• 100 Generic build failure

  The builder process returned with a non-zero exit code.

• 101 Build timeout

  The build was aborted because it did not complete within the specified timeout.

• 102 Hash mismatch

  The build output was rejected because it does not match the outputHash attribute of the derivation.

• 104 Not deterministic

  The build succeeded in check mode but the resulting output is not binary reproducible.

With the --keep-going flag it's possible for multiple failures to occur. In this case the 1xx status codes are or combined using bitwise OR.

0b1100100
     ^^^^
     |||`- timeout
     ||`-- output hash mismatch
     |`--- build failure
     `---- not deterministic