How to change Xcode/CLT version in CI/Github Actions

[Joshua Root]

On 21/11/2023 12:51, Dave Allured - NOAA Affiliate via macports-dev wrote:
> Is there an easy way to select a specific Xcode or CLT version for CI 
> workflows?  Developers could insert such temporary control into 
> individual PR's, to be excluded upon merging.   Alternatively, Macports 
> could insert this into macports-ports/master for community benefit, 
> while we ride out the wait for Apple fixes or other solutions.

Any problems seen on CI due to Xcode 15 will also be seen by end users 
running that Xcode version. So any necessary workarounds should be 
applied in ports based on $xcodeversion and/or $xcodecltversion.

It's probably possible to install a different Xcode version as part of 
the CI bootstrap script, but that would eat up a lot of build minutes 
and would just be hiding the problems that users will be seeing if 
they're not worked around.

- Josh