Disable `mmap` in `libbacktrace` on Apple platforms

Disable `mmap`  in `libbacktrace` on Apple platforms

Fixes #45731

libbacktrace uses mmap if available to map ranges of the files containing debug information. On macOS `mmap` will succeed even if the mapped range does not exist, and a SIGBUS (with an unusual EXC_BAD_ACCESS code 10) will occur when the program attempts to page in the memory. To combat this we force `libbacktrace` to be built with the simple `read` based fallback on Apple platforms.