CI tests silently failing, possibly due to a rustc nightly update

[48cf]

Parts of Aero are failing to build on rustc 1.59.0-nightly (23f69235a 2021-12-20) with a following ICE: https://gist.github.com/czapek1337/7a3d0c7fa3381195604947e9e1c809a0

I've had both kernel and userland fail to build now. The problem is on a clean build cargo doesn't report that ICE, or we just silently ignore it in aero.py, on subsequent runs it's reported correctly. Due to that our CI tests seem to fail silently. A temporary fix to that is to use the --release cargo flag, but we should definitely investigate as to why that happens and possibly report that as a compiler bug.

[48cf]

Update: it looks like commits between rust-lang/rust@e95e084 (last recorded working nightly) and rust-lang/rust@23f6923 (current nightly) contain a change that causes this behavior.