clang-tidy: run tool only on source files participating in targets

[Sahnvour]

clang-tidy can't be ran as is on every source file and header

closes #7662

[dcbaker]

Code looks good. This should have release snippet and if we have any documentation on the clang-tidy target elsewhere, that needs an update.

[Sahnvour]

I'm not aware of documentation on this feature, only saw it in the release notes.
I don't know how release snippets work, are you expecting something from me?

[dcbaker]

A release snippet is just a small bit off markdown that goes in docs/markdown/snippets. When the release is made all of those snippets get gathered up into the "what changed" page. I'd like if you could add something there with this to alert people of this change (it may be surprising to some people).

I also don't seen any generic documentation on the clang-tidy target, so no need to worry about that.

[Sahnvour]

Updated with snippet.

[dcbaker]

Thanks!