There is an updated pull request by jnbr against master on the void-packages repository

https://github.com/jnbr/void-packages firefox-69
https://github.com/void-linux/void-packages/pull/14195

firefox: update to 69.0.
Todo:

- [x] build and test on some architectures
- [x] adopt latest changes from thunderbird template

A patch file from https://github.com/void-linux/void-packages/pull/14195.patch is attached