backuptool: Preserve symlinks

Without -d, we copy the file sysmlinked rather than the symlink.

Change-Id: Ie0fdd43f29e53334464188c846dd7a3b7bb770cc
diff --git a/prebuilt/common/bin/backuptool.functions b/prebuilt/common/bin/backuptool.functions
index 6d128d7..71a648c 100644
--- a/prebuilt/common/bin/backuptool.functions
+++ b/prebuilt/common/bin/backuptool.functions
@@ -16,7 +16,7 @@
       echo "Skipping odexed apk $1";
     else
       mkdir -p "$C/$D"
-      cp -p $1 "$C/$D/$F"
+      cp -dp $1 "$C/$D/$F"
     fi
   fi
 }
@@ -28,7 +28,7 @@
     if [ ! -d "$DIR" ]; then
       mkdir -p "$DIR";
     fi
-    cp -p "$C/$DIR/$FILE" "$1";
+    cp -dp "$C/$DIR/$FILE" "$1";
     if [ -n "$2" ]; then
       echo "Deleting obsolete file $2"
       rm "$2";