Rust is moving rather fast, and doing "raw" squeekboard builds using Cargo fails (see https://gitlab.gnome.org/World/Phosh/squeekboard/-/merge_requests/561 ).
This will make it difficult to folks to hack on Squeekboard using PureOS, which is something I'd prefer to avoid.
The alternative way to avoid that is to lock dependency versions in Squeekboard, but I would prefer to give folks in general access to newer Rust, and to be able to move the project itself to newer features.
It pains me that folks won't be able to just do meson builds of Squeekboard, so I'm currently trying to check how many packages need to be imported from bookworm to Byzantium to get a high enough rustc version.
I've investigated what is needed to build rustc, and so far:
```
builddeps:. : Depends: rustc (>= 1.58.0+dfsg)
Depends: llvm-13-dev but it is not installable
Depends: llvm-13-tools but it is not installable
Depends: libllvm13 (>= 1:13.0.0) but it is not installable
Depends: wasi-libc (>= 0.0~git20210922.ad51334~~) but 0.0~git20200731.215adc8-2 is to be installed
Depends: clang-13 but it is not installable
```
Out of those, rustc is a recursive-ish dependency, and llvm can be built without further changes.