again same 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`

error[E0463]: can't find crate for `compiler_builtins`

error[E0463]: can't find crate for `core`
   --> /home/fly/.cargo/registry/src/index.crates.io-6f17d22bba15001f/bitflags-1.3.2/src/lib.rs:282:1
    |
282 | pub extern crate core as _core;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate
    |
    = note: the `thumbv7m-none-eabi` target may not be installed
    = help: consider downloading the target with `rustup target add thumbv7m-none-eabi`

For more information about this error, try `rustc --explain E0463`.
error: could not compile `bitflags` (lib) due to 3 previous errors
warning: build failed, waiting for other jobs to finish...
info: installing component 'rust-src'
error: component download failed for rust-src: could not rename downloaded file from '/home/fly/.rustup/downloads/43b2187da2752307fb710914805cb685b35308acb22413f1616ad04448a598f1.partial' to '/home/fly/.rustup/downloads/43b2187da2752307fb710914805cb685b35308acb22413f1616ad04448a598f1'
error: could not compile `proc-macro2` (build script)
mommy knows you're feeling down, but you'll get through it~ ❤️
fly@tuxtop:~/embassy/examples/stm32f1$ rustup target add thumbv7m-none-eabi
info: component 'rust-std' for target 'thumbv7m-none-eabi' is up to date

```