In your CMakeLists.txt, do:
ADD_CUSTOM_TARGET(your_edj_file.edj
COMMAND edje_cc your_edc_file.edc your_edj_file.edj
)
Notice that I simplified the COMMAND line - add the same arguments you use when you run edje_cc on a terminal (e.g. -id for images dir, -fd for fonts dir).
With this line added to CMakeLists.txt, a call to cmake in your packaging.spec file should be enough.