Interesting, I'd heard of buck and classified it as a blaze/bazel clone made by Xooglers who ended up at Facebook. But didn't realize buck2 was written in Rust.
One of the specific weaknesses I found with Bazel for embedded development was support for multiple toolchains was really not great. I'm sure it's improved, but I found the gn/ninja combination much better.
However, I'm procrastinating right now by reading HN instead of fixing our multi-compiler requirement toolchain setup for Bazel, and I am contemplating resigning from my job and IT altogether. I hate Bazel at this point.
I would suggest Buck2 (which is written in Rust, so you can use the existing tooling to build it) https://buck2.build/ https://github.com/facebook/buck2
Rust support is also rather good ;) https://github.com/facebookincubator/reindeer But you need "fixups" to get many cargo packages to work with Buck 2: https://github.com/facebook/buck2/tree/main/shim/third-party...