lxc-setcap: use POSIX shell instead of bash

src/lxc/lxc-setcap.in

-#!/bin/bash
+#!/bin/sh
 
 #
 # lxc: linux Container library
@@ -81,31 +81,39 @@ lxc_dropcaps()
     chmod 0755 @LXCPATH@
 }
 
-shortoptions='hd'
-longoptions='help'
-
-getopt=$(getopt -o $shortoptions --longoptions  $longoptions -- "$@")
-if [ $? != 0 ]; then
+usage_err() {
+    [ -n "$1" ] && echo "$1" >&2
     usage
     exit 1
-fi
+}
 
-eval set -- "$getopt"
+optarg_check() {
+    if [ -z "$2" ]; then
+        usage_err "option '$1' requires an argument"
+    fi
+}
 
-while true; do
-    case "$1" in
+while [ $# -gt 0 ]; do
+    opt="$1"
+    shift
+    case "$opt" in
 	-d)
 	    LXC_DROP_CAPS="yes"
-	    shift
 	    ;;
 	-h|--help)
 	    help
 	    exit 0
 	    ;;
 	--)
-	    shift
 	    break
 	    ;;
+        -?)
+            usage_err "unknown option '$opt'"
+            ;;
+        -*)
+            # split opts -abc into -a -b -c
+            set -- $(echo "${opt#-}" | sed 's/\(.\)/ -\1/g') "$@"
+            ;;
          *)
 	    usage
 	    exit 1