[CMake] Dependencies scanning for non-c/c++ files

[Aaron_Wright at selinc.com]

I have some m4 files in my build that include other m4 files, so there's a 
dependency between m4 files that can change at any time. I can calculate 
the dependency at configure time, but what can I do when the files change 
and I need to recalculate the dependencies? This is obviously handled for 
c/c++ files by CMake. Any ideas?

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Aaron Wright