Bazel CI on macOS is flaky

[dtolnay]

https://github.com/dtolnay/cxx/actions/runs/5316243831/jobs/9625555063

Starting local Bazel server and connecting to it...
... still trying to connect to local Bazel server (2570) after 10 seconds ...
... still trying to connect to local Bazel server (2570) after 20 seconds ...
... still trying to connect to local Bazel server (2570) after 30 seconds ...
... still trying to connect to local Bazel server (2570) after 40 seconds ...
... still trying to connect to local Bazel server (2570) after 50 seconds ...
... still trying to connect to local Bazel server (2570) after 60 seconds ...
... still trying to connect to local Bazel server (2570) after 70 seconds ...
... still trying to connect to local Bazel server (2570) after 80 seconds ...
... still trying to connect to local Bazel server (2570) after 90 seconds ...
... still trying to connect to local Bazel server (2570) after 100 seconds ...
... still trying to connect to local Bazel server (2570) after 110 seconds ...
FATAL: couldn't connect to server (2570) after 120 seconds.

Behavior like this was reported in bazelbuild/bazel#14459 and, at least in that case, it sounds like it was related to the GitHub Actions environment in which xcode-locator is slow on a machine containing a large number of Xcode installations.

https://www.smileykeith.com/2021/03/08/locking-xcode-in-bazel/ was recommended as a workaround worth trying.