atmega-usbd toolchain: update to latest nightly

Nightly builds compile with the current version release (2023-05-15).

Adding codegen-units = 1 fixes compilation errors for debug builds.

See: https://github.com/rust-lang/compiler-builtins/issues/523#issuecomment-1547339559

May 16 '23 03:05 rmsyn

I can't compile with this version:

$ cargo +nightly-2023-05-15 b --release --example arduino_keyboard
...
LLVM ERROR: Expected a constant shift amount!

nightly-2023-03-24 works fine however.

Jul 16 '23 03:07 agausmann

I can't compile with this version

:facepalm: I added codegen_units = 1 to the wrong build profile. Fixed now.

The build also works with the latest nightly, so we could possibly change the toolchain in rust-toolchain.toml to just be nightly.

I also needed to change usbd-hid dev dependency to a git dependency. The latest nightlies break on a previous version of proc-macro2 that the latest published release of usbd-hid depends on.

Jul 18 '23 01:07 rmsyn