Merge branch 'unity-after-compile-features' into restore-pch-with-unity

Replace commit 76b5383123 (cmGlobalGenerator: add unity sources after
computing target compile features, 2024-01-01, v3.28.2~17^2~1) with an
alternative change.  This merge commit resolves conflicts such that
future `git blame` calls will follow the second parent for the relevant
lines and pretend the replaced commit never existed.

Fixes: #25650