The logic is that the describe output is readily available using `git
tag --contains` locally. In addition, for a hypothetical commit which
landed in both v3.9.4 and v3.10.1, there is no "better" tag to refer to.
since v3.10.0's relation to such a commit is unclear either way.

Also mention that a `Fixes` trailer is preferred if the mention is just
to indicate a commit which introduced an error rather than writing a
complete sentence about it.

This builder builds CMake using lint tools but does not run the test
suite.  Document it for reviewers to request with `Do: test -i lint`.

Add a dedicated subsection header for its documentation.

Fixes: #16264.