Since yesterday when the macOS VMs have been upgraded to 10.15 the macOS SDKs are missing but still present in the docs: https://help.github.com/en/actions/automating-your-workflow-with-github-actions/software-installed-o...
I'm also having issues with this -- I want to be able to target macOS 10.13 as the minimum version for builds, which is a problem when the SDK is nowhere to be found.
Some more detail of what I've tried in my quest to locate the missing SDKs. I've tried using xcode-select on the other XCode versions installed (11.0, 11.1) and `xcodebuild -showsdks` to see if they show something other than just 10.15. I also looked for a /Developer folder to see if there were SDKs there, but the folder doesn't exist.
Thanks for your feedback. This is an issue with the documentation. The SDKs were removed along with Xcode 9.* and Xcode 10.*, please refer to the changelog here for details. We will update the documenation to avoid the confusion.