ENH add the CDTs for qt 5.15

[beckermr]

Please see the repo readme for directions on how to make PRs on this repo.

Checklist:

• [x] if you have added a CDT, it appears in the cdt_slugs.yaml file and you have rerun the script python gen_cdt_recipes.py.
• [ ] if you have changed the CDT generator code (rpm.py), you have bumped the build number in conda_build_config.yaml and have remade all of the recipes via running python gen_cdt_recipes.py --force
• [ ] if you have added a custom CDT recipe, you have added the name of the CDT with custom: true in the cdt_slugs.yaml file.
• [ ] all CDT recipes have build number set by {{ cdt_build_number }} for old-style/legacy CDTs or {{ cdt_build_number|int + 1000 }} for new-style CDTs
• [ ] if you see a warning about a CDT not having a license, you have added the license_file key in the cdt_slugs.yaml file with the path to the appropriate license in licenses/

NOTE: If you make any changes to cd_slugs.yaml, you need to reun the generator code via python gen_cdt_recipes.py.

[beckermr]

@andfoy check if this PR has what you need. The code ran fine for me locally and put in the correct changes. I think something in your dev env is reformatting the YAML which is throwing off the code.

[andfoy]

@beckermr, thanks for the help with this one! The PR contains all the required packages. I'm going to close the other one