use debhelper 9 for xenial

Author: sorah

debian/changelog

@@ -20,11 +20,6 @@ ruby2.5 (2.5.0-0nkmi1) unstable; urgency=medium
     * debian/libruby2.5.symbols: update with symbols added/removed since the
       preview1 release
     * debian/tests/bundled-gems: handle extra field in gems/bundled_gems
-    * New upstream release candidate. Includes the following fixes:
-    * New upstream release candidate. Includes the following fixes:
-        built-in multiarch support as before debhelper compatibility level 9
-      preview1 release
-    * debian/tests/bundled-gems: handle extra field in gems/bundled_gems
 
  -- Sorah Fukumori <[email protected]>  Mon, 25 Dec 2017 15:05:33 +0000
 

debian/compat

@@ -1 +1 @@
-10
+9

debian/control

@@ -5,7 +5,7 @@ Maintainer: Sorah Fukumori <[email protected]>
 Build-Depends: bison,
                chrpath,
                coreutils (>= 7.5),
-               debhelper (>= 10),
+               debhelper (>= 9),
                file,
                libffi-dev,
                libgdbm-dev,