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

https://github.com/zdtcd/void-packages firefox
https://github.com/void-linux/void-packages/pull/15687

Firefox 70.0.0
Included 2 commits from #15686, since Firefox 70.0 requires nss 3.46.1

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Built for:
- [x] x86_64-musl
- [x] x86-64
- [x] i686
- [x] armv7
- [x] aarch64-musl

Tested with:
- [x] x86_64
- [x] x86_64-musl

A patch file from https://github.com/void-linux/void-packages/pull/15687.patch is attached