scripts: add comment to clarify usage

scripts/unpack

@@ -39,6 +39,7 @@ mkdir -p $BUILD
 STAMP_DEPENDS="$PKG_DIR $PKG_NEED_UNPACK $PROJECT_DIR/$PROJECT/patches/$PKG_NAME"
 [ -n "$DEVICE" ] && STAMP_DEPENDS="$STAMP_DEPENDS $PROJECT_DIR/$PROJECT/devices/$DEVICE/patches/$PKG_NAME"
 
+# Perform a wildcard match on the package to ensure old versions are cleaned too
 for i in $BUILD/$1-*; do
   if [ -d $i -a -f "$i/.libreelec-unpack" ] ; then
     . "$i/.libreelec-unpack"