The guard instruction for unreachables and other crashes in aarch64 is
`brk`, in macos there isn't a distinction between a brk for a breakpoint
and one for a crash, as an attempt we check the value of `pc` when the
signal is triggered, if it is
`brk #0x1` we say that it is a crash and go into the sigdie_handler. 

We should probably do the same in aarch64 linux, though I haven't dug
too deep into what values it uses for traps, and if what compiler used
matters, on apple I assumed we use clang/LLVM

It might be possible to test this by calling some inline assembly.

This means that something like
https://github.com/JuliaLang/julia/issues/51267 actually crashes with
```c
[16908] signal (5): Trace/BPT trap: 5
in expression starting at /Users/gabrielbaraldi/julia/test.jl:2
_collect at ./array.jl:768
collect at ./array.jl:757
top-level scope at /Users/gabrielbaraldi/julia/test.jl:5
_jl_invoke at /Users/gabrielbaraldi/julia/src/gf.c:2892
jl_toplevel_eval_flex at /Users/gabrielbaraldi/julia/src/toplevel.c:925
jl_toplevel_eval_flex at /Users/gabrielbaraldi/julia/src/toplevel.c:877
ijl_toplevel_eval at /Users/gabrielbaraldi/julia/src/toplevel.c:943 [inlined]
ijl_toplevel_eval_in at /Users/gabrielbaraldi/julia/src/toplevel.c:985
eval at ./boot.jl:383 [inlined]
include_string at ./loading.jl:2070
_jl_invoke at /Users/gabrielbaraldi/julia/src/gf.c:2873
ijl_apply_generic at /Users/gabrielbaraldi/julia/src/gf.c:3074
_include at ./loading.jl:2130
include at ./Base.jl:494
jfptr_include_46486 at /Users/gabrielbaraldi/julia/usr/lib/julia/sys.dylib (unknown line)
_jl_invoke at /Users/gabrielbaraldi/julia/src/gf.c:2873
ijl_apply_generic at /Users/gabrielbaraldi/julia/src/gf.c:3074
exec_options at ./client.jl:317
_start at ./client.jl:552
jfptr__start_83179 at /Users/gabrielbaraldi/julia/usr/lib/julia/sys.dylib (unknown line)
_jl_invoke at /Users/gabrielbaraldi/julia/src/gf.c:2873
ijl_apply_generic at /Users/gabrielbaraldi/julia/src/gf.c:3074
jl_apply at /Users/gabrielbaraldi/julia/src/./julia.h:1970 [inlined]
true_main at /Users/gabrielbaraldi/julia/src/jlapi.c:582
jl_repl_entrypoint at /Users/gabrielbaraldi/julia/src/jlapi.c:731
Allocations: 570978 (Pool: 570031; Big: 947); GC: 1
fish: Job 1, './julia test.jl' terminated by signal SIGTRAP (Trace or breakpoint trap)
```
instead of hanging silently

---------

Co-authored-by: Jameson Nash <vtjnash@gmail.com>