Externalise cache keys to prevent unneeded invalidation

[pljones]

Short description of changes

I noticed whilst I've been working on autobuild.sh that every change invalidates all the caches. Because autobuild.sh itself is included in the cache key calculation. This change replaces that mechanism on macOS and Windows with am externalised list of dependencies. It adds the same mechanism to iOS, which lacked caching.

Github cache clean up will remove unused cache entries with no need to have the cache consumer included in the cache key.

(My work in progress on the Android build uses the same approach, which is where this comes from.)

Scope, guidance, testing and review by myself, coding my VSCode Github CoPilot.

CHANGELOG: Build: improve cache persistence

Context: Fixes an issue?

Caching should depend on what is being cached, rather than the cache consumer.

Does this change need documentation? What needs to be documented and how?

No.

Status of this Pull Request

Tested against the current branch in my own repository before raising the PR here.

What is missing until this pull request can be merged?

Need to do some more testing.

Checklist

• I've verified that this Pull Request follows the general code principles
• I tested my code and it does what I want
• My code follows the style guide
• I waited some time after this Pull Request was opened and all GitHub checks completed without errors.
• I've filled all the content above

AUTOBUILD: Please build all targets

[softins]

Looks ok in general, just a couple of comments.

[pljones]

Well, it's not quite there, is it....

[mcfnord]

🤖 AI: The four former param() defaults at deploy_windows.ps1 kept their trailing commas and deploy_mac.sh kept the ../.. that suits a script one level deeper, and two more sit behind that Windows parse error: the launch line still passes the two Qt paths positionally to a param() that no longer declares them, and $QtCompile64 is now msvc2022 while the aqt arch is still win64_${QtCompile64}_64.

[pljones]

Well, the cache keys and cache creation are working now. ios appeared to be a bit flaky - consistently failing to create the cache. I did a straight rerun under debug and... it worked. So I don't know why it wasn't working!

I've yet to test bump-dependencies with the new scheme. It actually makes it a lot simpler: it's just maintaining the version files based on the available version numbers. Unfortunately I've not managed to get it to run at all on my repo (even for main).

[pljones]

So I reran the iOS build to see if it used the cache:

/opt/homebrew/bin/gtar: ../../../../../opt/qt: Cannot mkdir: Permission denied

Oh well. But it does give useful information -- the other runs don't stick Qt under /opt, they use a project work directory. I'll see if I can get that working here, too.