[CMake] Creating file with dependencies

[Jon Schewe]

I recently started using cmake and find it generally to be a nice tool,
however I'm rather frustrated with it now. Can someone please tell me
how to get cmake to conditionally create a file as part of executing a
target? What I want to do looks like this, but apparently
add_custom_command only can execute shell scripts, so I'm not sure how
one can use these nice commands for writing files.

FUNCTION(build_includes)
  FILE(WRITE unit_test_includes.hpp "// Autogenerated - do not edit\n")
  FOREACH(test ${TESTS})
    FILE(APPEND unit_test_includes.hpp "#include \"${test}\"\n")
  ENDFOREACH(test)
ENDFUNCTION(build_includes)


ADD_CUSTOM_COMMAND(OUTPUT unit_test_includes.hpp
                           COMMAND build_includes
                                     DEPENDS ${TESTS}
                                     COMMENT "Building
unit_test_includes.hpp"
                                     )

And then unit_test_includes.cpp is included in one of my hand written
cpp files that is used to build the target.

Of course what doesn't work is the COMMAND of ADD_CUSTOM_COMMAND. How
does one do this with cmake? I'd rather not write the shell script to do
this because then it won't work on Windows systems.

-- 
Jon Schewe | Research Scientist
BBN Technologies | http://www.bbn.com
952-545-5720 - Office
612-210-8818 - Cell