Bugfix: avoid clobbering of valid variants when a config key contains a superset of values of the same key in a lower priority cbc.yaml

[danpetry]

Description

Fixes #5038

When higher priority cbc.yamls contain, for a certain config entry, a superset of values that are in a lower priority cbc.yaml, the extra values get ignored. For example, if you have in a feedstock's conda_build_config.yaml

openssl:
  - 1.1.1
  - 3.0

and in aggregate/conda_build_config.yaml

openssl:
  - 3.0

I would expect two versions of the package is build, but only the one with openssl 3.0 is built.

When a zip_keys entry is used in the feedstock's cbc.yaml, the keys get zipped, but then the variants without the entry from the aggregate cbc.yaml gets clobbered.

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[conda-bot]

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[travishathaway]

@conda-bot check

[danpetry]

Hi @travishathaway or @kenodegard or other? It would be nice to get some eyes on this if possible - we're affected by this relatively frequently in the packaging team

[danpetry]

Thanks @kenodegard ! how many approvals required to merge?