[CMake] Adding non-build-related sources to IDE projects

[Bryan O'Sullivan]

Is there an appropriate way to cause an IDE like Visual Studio or Xcode 
to present entries for source files such as .h files and .xml files, 
which do not get compiled?

I'm currently listing those files as sources for library and executable 
targets.  This doesn't work very well: I have to make sure I'm not 
generating a Makefile, because then the files are listed in the Makefile 
rule and cause compilation to fail.  Under Xcode, doing this causes lots 
of build warnings as xcodebuild complains that it has no rules for .txt 
or .xml files.

Is there a better way?

	<b