Vanilla rsync in macOS is not new enough to run bsync

[jfding]

Noticed that bsync require the "rsync protocol version" need to higher or equal to "30", while the vanilla rsync command in macOS is "29". So bsync cannot work o macOS actually.

We do have the solution to fix it, by "brew install rsync" to use the latest version from homebrew repo.

My macOS version is "Sonoma 14.6.1", on "Apple Silicon"(ARM64) hardware.

[jfding]

I will have a patch to check the rsync/protocol version and prompt the 'brew install' reminding to user, to avoid new user pending on this issue.