build.yml: Report failures (e.g. from incremental test) earlier #35814
Description
as suggested in #35652 (comment)
possibly using https://github.com/LouisBrunner/checks-action
and/or problem matchers for:
- sphinx (see https://github.com/python/cpython/pull/20325/files)
- linter errors
- doctest failures