cp -r -L is illegal on iOS

Change-Id: I802709d45ebe26d5964633672fcbc2439a03d3f7
diff --git a/bucklets/onos.bucklet b/bucklets/onos.bucklet
index b2556c9..f34e657 100644
--- a/bucklets/onos.bucklet
+++ b/bucklets/onos.bucklet
@@ -317,7 +317,7 @@
    ):
 
    cmd = ( 'mkdir -p $TMP/%(root_dir)s && '
-           'cp -r -L $SRCDIR/* $TMP/%(root_dir)s && '
+           'cp -R -L $SRCDIR/* $TMP/%(root_dir)s && '
            'tar -C $TMP -zcf $OUT %(root_dir)s' ) % {
            'root_dir': root if root is not None else name
          }