fails with different error:
```
error[E0463]: can't find crate for `core`
  |
  = note: the `thumbv7m-none-eabi` target may not be installed
  = help: consider downloading the target with `rustup target add thumbv7m-none-eabi`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

For more information about this error, try `rustc --explain E0463`.
error: could not compile `bitflags` (lib) due to previous error

```