I made new licenses [1] [2] that attempt this. The problem with adding a clause against ML training is that that is (supposedly) fair use. What my licenses do is concede that but claim that the output of those algorithms is still under the copyright and license.

I hope that even if it wouldn't work, it puts enough doubt in companies' minds that they wouldn't want to use a model trained by code under those licenses.

[1]: https://gavinhoward.com/2021/07/poisoning-github-copilot-and...

[2]: https://yzena.com/licenses/