MDEV-7351 5.5 build fails on Ubuntu Utopic in buildbot

include oqgraph into deb packages conditionally, just like we do with tokudb

debian/dist/Debian/mariadb-server-5.5.files.in

 usr/lib/mysql/plugin/ha_innodb.so
-usr/lib/mysql/plugin/ha_oqgraph.so
 usr/lib/mysql/plugin/sphinx.so
 usr/lib/mysql/plugin/auth_socket.so
 usr/lib/mysql/plugin/auth_pam.so
@@ -73,3 +72,4 @@ usr/share/mysql/mysql_system_tables.sql
 usr/share/mysql/mysql_performance_tables.sql
 usr/share/mysql/mysql_test_data_timezone.sql
 @TOKUDB_DEB_FILES@
+@OQGRAPH_DEB_FILES@

debian/dist/Ubuntu/mariadb-server-5.5.files.in

 usr/lib/mysql/plugin/ha_innodb.so
-usr/lib/mysql/plugin/ha_oqgraph.so
 usr/lib/mysql/plugin/sphinx.so
 usr/lib/mysql/plugin/auth_socket.so
 usr/lib/mysql/plugin/auth_pam.so
@@ -75,3 +74,4 @@ usr/share/mysql/mysql_system_tables.sql
 usr/share/mysql/mysql_performance_tables.sql
 usr/share/mysql/mysql_test_data_timezone.sql
 @TOKUDB_DEB_FILES@
+@OQGRAPH_DEB_FILES@

storage/oqgraph/CMakeLists.txt

@@ -52,4 +52,5 @@ IF(BOOST_OK)
 
   MYSQL_ADD_PLUGIN(oqgraph ha_oqgraph.cc graphcore.cc STORAGE_ENGINE
                    MODULE_ONLY)
+  SET(OQGRAPH_DEB_FILES "usr/lib/mysql/plugin/ha_oqgraph.so\n" PARENT_SCOPE)
 ENDIF(BOOST_OK)