Performance issue with macOS remote-debugging

I noticed two issues that cause a significant slow down during launch while during macOS debugging.

1. The file being debugging is always copied to the remote system despite the file with the same MD5 already exists on the remote system.
2. LLDB reads libobjc.A.dylib from memory. This is evident by the warning message during launch:

libobjc.A.dylib is being read from process memory. This indicates that LLDB could not find the on-disk shared cache for this device. This will likely reduce debugging performance.

I suppose this is caused by the shared cache mechanism on macOS, and libobjc.A.dylib does not exist on disk as a single file, so LLDB does not have a way to read it from disk. So it has to read it from memory. This causes a significantly slow down, often times to the scale of 20+ seconds. It appears that reading from the memory is also slower, potentially because once the file gets mapped, it takes more memory bytes (e..g, the .bss section will actually take space now)

Start by reproducing macOS remote-debugging launch delays and inspect the two reported paths: repeated file copies despite matching MD5 values and LLDB's libobjc.A.dylib shared-cache warning. No files or tests are named; done means avoiding unnecessary transfers and preventing or accounting for the slow memory-based library read.