fix(alias): ls alias lx is an illegal option on MacOS/BSD

The option `-X` lets MacOS (and probably also other BSD-ish OS) ls
complain about an illegal option:

```
ls -lhXB
ls: illegal option -- X
usage: ls [-ABCFGHLOPRSTUWabcdefghiklmnopqrstuwx1] [file ...]
```

modules/utility/init.zsh

@@ -118,7 +118,9 @@ alias ll='ls -lh'        # Lists human readable sizes.
 alias lr='ll -R'         # Lists human readable sizes, recursively.
 alias la='ll -A'         # Lists human readable sizes, hidden files.
 alias lm='la | "$PAGER"' # Lists human readable sizes, hidden files through pager.
-alias lx='ll -XB'        # Lists sorted by extension (GNU only).
+if [[ "$OSTYPE" != darwin* ]]; then
+  alias lx='ll -XB'        # Lists sorted by extension (GNU only).
+fi
 alias lk='ll -Sr'        # Lists sorted by size, largest last.
 alias lt='ll -tr'        # Lists sorted by date, most recent last.
 alias lc='lt -c'         # Lists sorted by date, most recent last, shows change time.