Fix permissions when openrsync is used

[mjburghard]

Fix file permissions when openrsync is used on macOS 14.5+.

What was changed

Apply write permission using find & chmod when running on macOS 14.5+. To mitigate any previous bazel run invocations that already left the temporary directory without write permissions, an additional check and call to fix the permissions is added before calling rsync. This is needed when rsync needs to delete or modify any existing files.

Why was this changed

macOS 15.4.1 replaced the rsync implementation with openrsync. Apple seems to have added some additional flags like --chmod to openrsync to match the functionality and interface of rsync. Unfortunately, not there are bugs like --chmod being not properly applied when syncing directories.

How to test

• macOS 15.4+ is required
• Run bazelisk run //examples/ios/HelloWorld --define=apple.experimental.tree_artifact_outputs=1. simctl should fail with a permission error. (If this steps succeeds, delete the temporary directory and uninstall HelloWorld from the iOS simulator).
• Switch to this PR and rerun the command. The command should succeed.

[mjburghard]

Adding --perms since the man page says it is required when passing --chmod.
Does not have any observable effect at the moment.