Inline conda_build_config values to rattler-build recipes

[gforsyth]

As noted in rapidsai/rmm#1796 (comment)
the RAPIDS conda builds do not use variants (excepting ucxx)

We currently list the variants because the compiler version is dependent on the
CUDA version. This restriction will go away once we drop CUDA 11 support. At
that point, we should stop using the conda_build_config.yaml files and inline
the values there into the recipe.yaml file.

[jameslamb]

we should stop using the conda_build_config.yaml files and inline the values there into the recipe.yaml file

Do recipes written for rattler-build support some way to set re-usable values?

Like can those recipes use YAML anchors or passed-in variables or Jinja set statements or something?

Asking because conda_build_config.yaml is serving that purpose for some RAPIDS recipes right now. For example, look at libraft: https://github.com/rapidsai/raft/blob/f089d1cd207dbc2784c71d0f392c0f1e6e1bc4f3/conda/recipes/libraft/meta.yaml

It uses conda_build_config.yaml to reduce duplication between things that need to be the same, to reduce the risk of "these 2 things are inconsistent" types of bugs.

For example, in conda_build_config.yaml:

cuda11_libcurand_run_version:
  - ">=10.2.5.43,<10.3.1"

(raft/conda/recipes/libraft/conda_build_config.yaml)

And in meta.yaml:

- libcurand {{ cuda11_libcurand_run_version }}
- libcurand-dev {{ cuda11_libcurand_run_version }}

(raft/conda/recipes/libraft/meta.yaml)

Just commenting to challenge the assumption that conda_build_config.yaml is used only for building variants. I hope we don't lose this ability to ensure consistency across things that need to be identical as RAPIDS recipes change to support rattler-build.

[gforsyth]

Like can those recipes use YAML anchors or passed-in variables or Jinja set statements or something?

Yeah, we can set these in the context at the top of the recipe

[vyasr]

For the record, this is equally possible with the legacy conda-build recipe format using top-level Jinja variables (like we do for the version etc). We simply chose not to do it that way (the decision predates me so I don't actually know why).