error: unexpected `--cfg ub_checks` flag
   |
   = note: config `ub_checks` is only supposed to be controlled by `-Z ub-checks`
   = note: manually setting a built-in cfg can and does create incoherent behaviors
   = note: `#[deny(explicit_builtin_cfgs_in_flags)]` on by default

error: aborting due to 1 previous error