title: Only run C preprocessor in cmake?
body: <p>I'm trying to use cmake to simplify distributing my OpenCL program. I have a kernel file which includes several headers and other source files, and I want to have a single self contained executable.</p>
  
  <p>My plan is to have cmake run the <strong>C</strong> preprocessor on the kernel source, turning the cl file and its includes into a single unit which is easier to work with.</p>
  
  <p>I can use add_custom_command to do it by calling gcc/clang with -E, but then I don't get the flags to include the right directories to find the various header files in the command, and I don't see an easy way to find all current include directories to use in the custom call to the compiler.</p>
  
  <p>Is there a way to run only the <strong>C</strong> preprocessor on a file with the current cmake environment?</p>