Help: Clarify add_custom_command DEPENDS conversion to file paths
In !4148 (merged) we updated the documentation to describe the behavior introduced by that MR. However, the behavior was removed again by !4195 (merged) without updating the documentation.
Update the documentation again to describe the behavior as of the latter MR. Spell out the steps that cmLocalGenerator::GetRealDependency
and cmTargetTraceDependencies::IsUtility
use to add file-level and target-level dependencies.
Backport: release