Make .rh files dependent on their contents (maybe they should be deps of the .rc file?)
Make .rh files dependent on the .mk file that their item lists come from
Fix .rh files not creating destination directory
Fix .rh dependencies of .rc file being source-relative instead of build-relative
Fix .rh clean paths being source-relative instead of build-relative
Fix .rh generation appending to the old .rh instead of overwriting