[CMake] Dependency checker

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Benjamin,

> Thank you for your quick answer. I had a quick glance - what I don't
> quite understand is how can I integrate this into my custom cmake
> script? I have a ADD_CUSTOM_COMMAND, and in the depends I need this list
> of dependent files (the generated files, not the xsd's themselves).
> 
> If you could shed some light on this, that would be very helpful

I have done something similar (with a different file type).  The low tech 
solution is to use "file(READ ${fileName} fileContents)" to get the contents of 
the file, and then search through the file contents for dependencies.  Another 
option that might work would be "file(STRINGS" with the REGEX option in order 
to reduce the resulting matches.

You can then use "string(REGEX MATCH" to search through the file contents for 
the dependency match and then add the dependency to "DEPENDS" in your 
add_custom_command.

This approach does not read the XML, but it should work as long as you can 
create a reasonable regular expression to find the dependencies in the file.

A more complicated option would be to create a separate application that reads 
the file and prints a list of dependencies.  You could then wrap that 
executable in a custom command and parse the results into your dependency 
list.

Respectfully,
Justin