CI: fix fast build

The cdash_handler.py script now uses environment variables as default. It will make it easier to launch it on windows (no need to replace all arguments $CI_XXX with %CI_XXX%.

The ref_name is properly detected: CI_MERGE_REQUEST_REF_PATH if merge request pipeline, CI_COMMIT_REF_NAME otherwise.

Also, a compilation fix in the new CosmoSkymed model, to make it compile with Ossim 2.2