Correct non unix to use an enum

[Blisto91]

Makes it so master can be compiled on windows.

Edit: I missed you removed these from the unix path. But dunno if you want the same here.

let cmd_name = action.build_kind.exec_command();
info!("running `cargo {}`", cmd_name);

Edit 2: I went ahead and removed the lines above as in the unix path

[fornwall]

Thanks!