Replay osx support

[joshuacolvin0]

If using MacOS, cargo stylus replay needs to use rust_lldb instead of rust_gdb

[gligneul]

LGTM!

Tested on macos and it works

(lldb) br set -f lib.rs -l 50
Breakpoint 2: where = libstylus_hello_world.dylib`stylus_hello_world::Counter::set_number::hff6961d5fa7cb04d + 24 at lib.rs:50:9, address = 0x0000000101a17a6c
(lldb) c
Process 62424 resuming
Process 62424 stopped
* thread #1, name = 'main', queue = 'com.apple.main-thread', stop reason = breakpoint 2.1
    frame #0: 0x0000000101a17a6c libstylus_hello_world.dylib`stylus_hello_world::Counter::set_number::hff6961d5fa7cb04d(self=0x000000016fdf6c00, new_number=Uint<256, 4> @ 0x000000016fdf6f70) at lib.rs:50:9
   47
   48  	    /// Sets a number in storage to a user-specified value.
   49  	    pub fn set_number(&mut self, new_number: U256) {
-> 50  	        self.number.set(new_number);
   51  	    }
   52
   53  	    /// Sets a number in storage to a user-specified value.
(lldb) p new_number
(ruint::Uint<256, 4>) {
  limbs = {
    [0] = 10
    [1] = 0
    [2] = 0
    [3] = 0
  }
}