sudo brew install qt@5 takes forever

I try to add macOS support for bazel_rules_qt [here](https://github.com/justbuchanan/bazel_rules_qt/pull/38).

To ensure this does not break in the future I added also a CI check for this to my PR.

In the CI job I try to install Qt5 using Homebrew. The job runs for more than 1 hour:
https://buildkite.com/bazel/rules-qt/builds/385#e814ad0e-436c-40ec-8c16-8680dc54db98

In a previous job run I canceled the job after 2 hours.
For some reason the command seems not to work or is very, very slow. Any hints form me how to make this faster?

Start with the linked Buildkite job and the CI step that runs `sudo brew install qt@5`; compare it with the earlier canceled run. Done means identifying why the Qt 5 installation stalls in CI and recording or implementing a reliable way for the macOS check to complete.

Written by the indexing model from the issue text.