```
Reasoning:
10.10 has been unsupported since July 2017 (~3 years at v0.20.0
release)
10.11 has been unsupported since July 2018 (~2 years at v0.20.0
release)
macOS users are consistent at upgrading to new releases.
Qt 5.12 LTS only supports macOS > 10.12. As long as we're supporting
macOS < 10.12 we would not be able to bump Qt in depends to 5.12 for the
v0.20.0 release.
```
Backport of core PR17550.