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

qt5: update to 5.15.2.
https://github.com/void-linux/void-packages/pull/26574

Description:
Todo:
- [x] fix qt5-webengine cross builds
- [x] rebase ppc patchset

Test repos:
https://void.johnnynator.dev/qt5.15.2/
https://void.johnnynator.dev/qt5.15.2-sndio/

Key fingerprint: `6b:7e:bd:35:60:20:08:e9:5a:f5:8b:ad:32:f9:a4:42`