There's a merged pull request on the void-packages repository

Thunderbird 78.6.1
https://github.com/void-linux/void-packages/pull/28028

Description:
<!-- Mark items with [x] where applicable -->

#### General
- [ ] This is a new package and it conforms to the [quality requirements](https://github.com/void-linux/void-packages/blob/master/Manual.md#quality-requirements)

#### Have the results of the proposed changes been tested?
- [x] I use the packages affected by the proposed changes on a regular basis and confirm this PR works for me
- [ ] I generally don't use the affected packages but briefly tested this PR

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#### Does it build and run successfully?

- [x] I built this PR locally for my native architecture, (x86_64-musl)
- [x] I built this PR locally for these architectures (if supported. mark crossbuilds):
  - [x] aarch64-musl
  - [x] armv7l
  - [x] armv7l-musl

[ci skip]

This PR is opened to be merged after we are done with new toolchains. Cross builds have been tested with GCC 10 and glibc 2.32 where applicable.