Investigate github cache reduction

[Mirko-von-Leipzig]

Keeping our CI cache usage low is an ongoing battle.

A couple of ideas to overall build size are mentioned here https://blog.rust-lang.org/2025/09/10/rust-compiler-performance-survey-2025-results. I recommend reading through the report in general, but I'm specifically interested in investigating the impact of:

1. -Zembed-metadata which is unfortunately +nightly but it would be interesting to know how much of a difference this makes.
2. Create (and use) a ci rust profile which disables (or reduces) debuginfo as per https://blog.rust-lang.org/2025/09/10/rust-compiler-performance-survey-2025-results/#debug-information. We can also consider updating dev similarly.
3. It may be useful to apply (2) to only our dependencies since only those are cached in github.

[bobbinth]

Could we increase the amount of cache that we have available to us? (I haven't checked yet myself, but maybe there is way to do it for some extra money)

[Mirko-von-Leipzig]

Could we increase the amount of cache that we have available to us? (I haven't checked yet myself, but maybe there is way to do it for some extra money)

afaik the answer is no. There is no mention of it anywhere in the docs https://docs.github.com/en/actions/reference/workflows-and-actions/dependency-caching#usage-limits-and-eviction-policy, nor have I come across any elsewhere.

What we could do is create an sccache on an S3 bucket which we could use across the org. That's a separate kind of problem, but might be worth it. Would also be useful for local development iiuc but now we're talking devops again 🤷