ci : add --symlinks to xcframework zip command (#12409)
This commit adds the --symlinks option to the zip command used to create
the xcframework zip file. This is necessary to create symlinks in the
zip file. Without this option, the Versions symlink is stored as a
regular directory entry in the zip file, rather than as a symlink in the
zip which causes the followig error in xcode:
```console
Couldn't resolve framework symlink for '/Users/danbev/work/ai/llama.cpp/tmp_1/build-apple/llama.xcframework/macos-arm64_x86_64/llama.framework/Versions/Current': readlink(/Users/danbev/work/ai/llama.cpp/tmp_1/build-apple/llama.xcframework/macos-arm64_x86_64/llama.framework/Versions/Current): Invalid argument (22)
```
Refs: https://github.com/ggml-org/llama.cpp/pull/11996#issuecomment-2727026377
