scripts/unpack: add (initial) support to handle 'zip' archives

Signed-off-by: Stephan Raue <stephan@openelec.tv>

scripts/extract

@@ -56,6 +56,10 @@ for i in $PKG_URL; do
         mkdir -p $3/$1
         7z x -o$3/$1 $f
         ;;
+      *.zip)
+        mkdir -p $3/$1
+        unzip -q $f -d $3/$1
+        ;;
       *.diff | *.patch)
         cat $f | patch -d $3 -p1
         ;;