Switch to compat 12. Remove vestiges of stretch support.

This switches us to using dh_installsystemd, and fixes some
service-restart-on-upgrade paths.

compat 12 was introduced in buster, so this won't work on
stretch, but we no longer support stretch so that's OK.

debian/compat

@@ -1 +1 @@
-10
+12

debian/control

@@ -2,7 +2,7 @@ Source: dump1090-fa
 Section: embedded
 Priority: extra
 Maintainer: Oliver Jowett <[email protected]>
-Build-Depends: debhelper(>=10),
+Build-Depends: debhelper(>=12),
   librtlsdr-dev <!custom> <rtlsdr>,
   libbladerf-dev <!custom> <bladerf>,
   libhackrf-dev <!custom> <hackrf>,
@@ -16,6 +16,7 @@ Vcs-Git: https://github.com/flightaware/dump1090.git
 
 Package: dump1090-fa
 Architecture: any
+Pre-Depends: ${misc:Pre-Depends}
 Depends: ${shlibs:Depends}, ${misc:Depends}, adduser, lighttpd
 Description: FlightAware ADS-B Ground Station System for SDRs
  Networked Aviation Mode S / ADS-B decoder/translator with support

debian/rules

@@ -62,8 +62,8 @@ override_dh_install:
 override_dh_installinit:
 	dh_installinit --no-restart-after-upgrade
 
-override_dh_systemd_start:
-	dh_systemd_start --no-restart-after-upgrade
+override_dh_installsystemd:
+	dh_installsystemd --no-restart-after-upgrade
 
 %:
-	dh $@ --with=systemd
+	dh $@

prepare-build.sh

@@ -38,11 +38,6 @@ cp -a $TOP/debian $OUT
 [ -d $TOP/debian-$DIST ] && cp -a $TOP/debian-$DIST/* $OUT/debian/
 
 case "$DIST" in
-    stretch)
-        echo "Updating changelog for stretch backport build" >&2
-        dch --changelog $OUT/debian/changelog --local ~bpo9+ --force-distribution --distribution stretch-backports "Automated backport build for jessie"
-        ;;
-
     buster)
         echo "Updating changelog for buster backport build" >&2
         dch --changelog $OUT/debian/changelog --local ~bpo10+ --force-distribution --distribution buster-backports "Automated backport build for buster"