Fix some issues building for Library Evolution, Xcode 16

[gemmakbarlow]

• Fixes some issues building for Library Evolution, Xcode 16
• Adds Makefile targets used to create the error state prior to fixing them
• Adjusts CI to incorporate both Xcode 15 and 16
• Adds Makefile target build-for-library-evolution to CI

[gemmakbarlow]

@stephencelis - this should be the last in the series from me 😄

[gemmakbarlow]

I also took a stab at updating CI to address the error from the previous run (not finding the 17.5 simulator with Xcode 16 selected IIRC). Let me know what you think; a couple of ways to do this.

[gemmakbarlow]

Noting that this is working for me locally @stephencelis - might be worth a re-run.

[gemmakbarlow]

@stephencelis - what do you think about giving this one a re-rerun, given it's working for me locally ? (I don't have that button available in the UI).

[stephencelis]

@gemmakbarlow I've been re-running but sadly GitHub actions just seem to be flakey. Here's hoping for a green run this time!

[stephencelis]

@gemmakbarlow Sorry for the churn. I'm frustrated with CI and I think some of the changes I've made to your PR have made things worse in how the simulator is getting resolved. I'm not sure if you want to take another stab at fixing things, or if you want me to try again when I have time.

[gemmakbarlow]

All good - I can take a stab at fixing it, hopefully later tonight.

[gemmakbarlow]

All good - I can take a stab at fixing it, hopefully later tonight.

Reader, she did not get back to it later tonight - but she is hoping to spend some time on this today / tomorrow.

[gemmakbarlow]

A workaround, as environment variables are not usable within a matrix, annoyingly.

[gemmakbarlow]

All good - I can take a stab at fixing it, hopefully later tonight.

Reader, she did not get back to it later tonight - but she is hoping to spend some time on this today / tomorrow.

@stephencelis - thrilled to report I finally got back to this, and things are working. Splitting out the library evolution builds into a separate job allowed for them to be run against a more appropriate matrix, and seems to have solved the iOS version / Xcode version issues we were seeing previously.

Further feedback welcomed.

[gemmakbarlow]

[gemmakbarlow]

Friendly bump on this one when you get a minute @stephencelis