In #2694, I updated Docker from 20.10 to 23.0, which was released in 2.309.0.

As mentioned at the top of the 23.0 release notes here, buildx was separated into a separate package in that release.

As a result of this change, we started experiencing the docker build issue below on our self-hosted runners after we updated them to 2.309.0:

• https://github.com/rapidsai/cuspatial/actions/runs/6385035317/job/17328916617?pr=1275#step:8:61

After further investigation, I noticed that Docker-Buildx was explicitly listed on the Installed Packages section of GitHub's runners below, which is likely why they weren't affected by this change:

• https://github.com/actions/runner-images/blob/main/images/linux/Ubuntu2204-Readme.md#tools

This PR installs buildx into the actions/runner images so that self-hosted runners can continue to function correctly.

cc: @Link-, @TingluoHuang