Determine systemd-sysv's upstart Conflicts: on build time

Use upstart-sysv when building on Ubuntu and upstart on Debian. This used to be
a delta in the Ubuntu branch, but breaks down when trying to do upstream build
tests with Debian's packaging in an Ubuntu VM (we can't yet run upstream tests
on Debian's CI).

debian/changelog

@@ -42,6 +42,8 @@ systemd (228-5) UNRELEASED; urgency=medium
   * debian/rules: If $TEST_UPSTREAM is set (when building/testing upstream
     master instead of distro packages), don't fail on non-installed new files
     or new library symbols.
+  * Determine systemd-sysv's Conflicts: on build time depending on whether
+    building on Ubuntu (upstart-sysv) or Debian (upstart).
 
   [ Michael Biebl ]
   * Drop support for the /etc/udev/disabled flag file. This was a workaround

debian/control

@@ -94,12 +94,12 @@ Multi-Arch: foreign
 Section: admin
 Priority: important
 Conflicts: sysvinit-core,
-           upstart,
+           ${conflicts:upstart},
            openrc,
            file-rc,
 Replaces: sysvinit (<< 2.88dsf-44~),
           sysvinit-core,
-          upstart
+          ${conflicts:upstart},
 Pre-Depends: systemd
 Depends: ${shlibs:Depends},
          ${misc:Depends}

debian/rules

@@ -8,8 +8,10 @@ VERSION = $(shell dpkg-parsechangelog | sed -n -e '/^Version:/s/.*: //p')
 
 ifeq ($(shell dpkg-vendor --query vendor),Ubuntu)
     DEFAULT_NTP_SERVERS = ntp.ubuntu.com
+    CONFLICTS_UPSTART = upstart-sysv, upstart (<< 1.13.2-0ubuntu10~)
 else
     DEFAULT_NTP_SERVERS = 0.debian.pool.ntp.org 1.debian.pool.ntp.org 2.debian.pool.ntp.org 3.debian.pool.ntp.org
+    CONFLICTS_UPSTART = upstart
 endif
 
 # fail on missing files and symbols changes on distro builds, but not if we
@@ -268,6 +270,9 @@ override_dh_autoreconf:
 override_dh_strip:
 	dh_strip --dbg-package=systemd-dbg
 
+override_dh_gencontrol:
+	dh_gencontrol -- -V'conflicts:upstart=$(CONFLICTS_UPSTART)'
+
 override_dh_auto_test:
 ifeq (, $(filter nocheck, $(DEB_BUILD_OPTIONS)))
 	# some tests hang under fakeroot, so disable fakeroot