Make the binary optional

1 job for master in 1 minute and 46 seconds
latest
Status Job ID Name Coverage
  Test
failed #28318
nightly

00:01:46

 
Name Stage Failure
failed
nightly Test

error: aborting due to 5 previous errors

Some errors have detailed explanations: E0432, E0433.
For more information about an error, try `rustc --explain E0432`.
error: could not compile `calculate`.

To learn more, run the command again with --verbose.
ERROR: Job failed: exit code 1