error: unexpected `--cfg fmt_debug="shallow"` flag
   |
   = note: config `fmt_debug` is only supposed to be controlled by `-Z fmt-debug`
   = 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