debian: Stop compressing the dpkg.deb package with gzip

There are only 5 remaining packages in the Debian base system that still
compress with gzip, the rest are all using xz, so there is no point in
making dpkg use gzip any longer.

debian/changelog

@@ -10,6 +10,7 @@ dpkg (1.18.11) UNRELEASED; urgency=medium
     - Use perl:Depends via dh_perl instead of a hardcoded perl in Depends.
     - Remove unused dh_strip from binary_indep target.
     - Remove ancient upgrade code from maintainer scripts (before 1.15.x).
+    - Stop compressing the dpkg.deb package with gzip.
   * Documentation:
     - Update custom changelog parser API support status in README.api.
     - Fix typos in docs and man pages. Thanks to Jakub Wilk <jwilk@debian.org>

debian/rules

@@ -121,10 +121,7 @@ binary-arch: install
 	dh_shlibdeps -a
 	dh_gencontrol -a
 	dh_md5sums -a
-	# Make debootstrap life easier on non-Debian based systems by
-	# compressing dpkg.deb with gzip instead of xz.
-	dh_builddeb -pdpkg -- -Zgzip
-	dh_builddeb -a -Ndpkg
+	dh_builddeb -a
 
 # Put together the dpkg-dev package
 binary-indep: install