take .apk file as optional param

xwords4/android/scripts/install_all.sh

@@ -6,7 +6,7 @@ APK=./bin/XWords4-debug.apk
 
 usage() {
     [ $# -ge 1 ] && echo "Error: $1"
-    echo "usage: $(basename $0) [-e] [-d]"
+    echo "usage: $(basename $0) [-e] [-d] [-p /path/to/.apk]"
     exit 1
 }
 
@@ -22,6 +22,11 @@ while [ $# -ge 1 ]; do
         -d)
             DEVICES="$DEVICES $(adb devices | grep -v emulator | grep 'device$' | awk '{print $1}')"
             ;;
+        -p)
+            [ $# -gt 1 ] || usage "-p requires an argument"
+            shift
+            APK=$1
+            ;;
         *)
             usage
             ;;