chore(ci): build channel from artifacts

[remimimimimi]

Problem

In the future we will have backends written in different languages which would require different dependencies. Current approach can't fulfill this, since we expect all binaries to be self-contained. It works for backends written in rust, but don't work for backends written in python for example.

Solution

Instead we can build conda packages from backends and pack them into temporary channel that will be stored in artifacts. This way in the pixi build testsuite we can augment manifests that we test with absolute path to this channel and therefore obtain latest backends required for testing.

[baszalmstra]

Is there are reason to disable this?

[remimimimimi]

Build of pixi-build-ros fails with mold, didn't investigated reasons though. I'll return back to this after CI will be green.

[Hofer-Julian]

Looks good!

[Hofer-Julian]

Schema is unhappy with this.

• If the schema's wrong -> fix the schema
• Otherwise fix this

[Hofer-Julian]

Maybe add the following to avoid rebuilds from scratch:

export CARGO_TARGET_DIR=${{ SRC_DIR }}/../../target-cache

[remimimimimi]

It seems to be invalidated between builds of recipe.

[remimimimimi]

I found a regression in compilation time. It seems that pixi-build-ros requires recompilation of rust part blowing up compilation time by the factor of 2. Reason is still unclear for me, but it works fine when I rebase my commits on top of #409. I'll start bisecting it.