Fix cargo audit workflow

The env context is only available at the step level, not the job one so
we need to use the github context instead. But the head_ref will only be
populated if we run in a pull_request event. So until we find a better
solution, let's match on the repo URL.

Fix clippy warnings.

Because of libtock-rs we can't run clippy on our codebase. But it could
run at least on `build.rs`.

Run everything that Travis-CI is running as Github workflows

These tests take 10 min. Let's avoid running them when not needed.

It seems the github action will pick up the rust-toolchain file and if
we specify it as an input, it will have a higher priority

Import bugfix from https://github.com/tock/tock/pull/1636 as a patch.

Fixed incorrect command in install.md.

`ioreg -P USB` doesn't work, it should be `ioreg -p USB` to get usb list in Mac OS X.

Synchronize with upstream Tock to remove 04-rtt.patch

Add Github workflows