Mac 12.6.8 nightlies are failing to generate the bundle

[Roboron]

EDIT: I found the root of the issue. See:
- https://github.com/Homebrew/homebrew-core/issues/140930
- https://github.com/actions/runner-images/issues/8078

We should probably just wait for this to be fixed by homebrew, or report the libraries affected if after some time it is not fixed.

Forcing brew to update in the GitHub CI currently fix libpng. Maybe we could build right now if compiling without fluidsynth (edit: yes we can).
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ORIGINAL POST

Mac nightlies are failing currently. Compilation succeeds, but bundling fails. The following warnings appear:

Code Select Expand

-- warning: embedded item does not exist '/Users/runner/work/simutrans-android/simutrans-android/build/opt/flac/lib/libFLAC.12.dylib'
--
warning: cannot resolve item '@loader_path/../../../../opt/flac/lib/libFLAC.12.dylib'

  possible problems:
    need more directories?
    need to use InstallRequiredSystemLibraries?
    run in install tree instead of build tree?
+11 similar warnings, and finally failing with:

Code Select Expand

   error:
  /Applications/Xcode_14.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/otool-classic:
  can't open file: @loader_path/../../../../opt/flac/lib/libFLAC.12.dylib (No
  such file or directory)
I have tried to find the cause of this problem, but without a Mac to work with and solely relaying on the GitHub pipelines is a pain in the ****, so help would be really appreciated.

Observations:

Last working run
- Link https://github.com/simutrans/simutrans/actions/runs/5877474466/job/15937673087
- MacOS version was 12.6.7
- Location of libFLAC resolved to '/usr/local/opt/flac/lib/libFLAC.12.dylib'
- Location of libpng (another of the libraries later failing to be bundled) resolved to '/usr/local/opt/libpng/lib/libpng16.16.dylib' during bundling.

First failed run
- Link https://github.com/simutrans/simutrans/actions/runs/6014305241/job/16313699535
- MacOS version is now 12.6.8
- Location of libFLAC resolved to '/Users/runner/work/simutrans-android/simutrans-android/build/opt/flac/lib/libFLAC.12.dylib' during bundling. Why this change? Is this related with this library finally throwing the error and not simply a warning like the others?
- Location of libpng resolved to '/usr/opt/libpng/lib/libpng16.16.dylib' during bundling (it is also on a different path from before, but no so drastic), similar for other libraries throwing a warning.