Add package spec files for 2018.4.0 release

The spec was in another branch at 2018.4.0 release date.

Change-Id: I0d78e38209cb09603ac727b9c15c50d06c8087eb
Closes-bug: PROD-28554
diff --git a/debian/gbp.conf b/debian/gbp.conf
new file mode 100644
index 0000000..d6f9d4f
--- /dev/null
+++ b/debian/gbp.conf
@@ -0,0 +1,8 @@
+[DEFAULT]
+upstream-branch = master
+debian-branch = debian/xenial
+upstream-tag = %(version)s
+compression = xz
+
+[buildpackage]
+export-dir = ../build-area/