gforth: mark as broken on darwin aarch64

The build fails with:
```
(vars) ./gforthmi gforth.fi  --die-on-signal -p ".:~+:." -i kernl64l.fi exboot.fs startup.fs arch/arm64/asm.fs arch/arm64/disasm.fs

Segmentation fault: 11.
```

pkgs/development/compilers/gforth/default.nix

@@ -41,6 +41,7 @@ in stdenv.mkDerivation rec {
     description = "The Forth implementation of the GNU project";
     homepage = "https://github.com/forthy42/gforth";
     license = lib.licenses.gpl3;
+    broken = stdenv.isDarwin && stdenv.isAarch64; # segfault when running ./gforthmi
     platforms = lib.platforms.all;
   };
 }