vtkWrapHierarchy is kept re-executed

[slicer]

vtkWrapHierarchy is kept re-executed

[lassoan]

@jcfr is it usual for a compiler/generator to only update timestamp of the output file if the content is changed? I can see that it can save time, but it is the root cause of the unnecessary regeneration of the hierarchy files at every build.

[mathstuf]

It only works if the build graph executor uses something like file content hashes to trigger reexecution. Timestamp-based systems (which is all CMake supports today) will need to update timestamps to avoid problems like this.