Try autostart JACK 2 different ways, one of them ought to work

Makefile

@@ -85,6 +85,7 @@ debug:
 
 install:
 	# Create directories
+	install -d $(DESTDIR)/etc/xdg/autostart/
 	install -d $(DESTDIR)$(PREFIX)/bin/
 	install -d $(DESTDIR)$(PREFIX)/share/applications/
 	install -d $(DESTDIR)$(PREFIX)/share/icons/hicolor/16x16/apps/
@@ -119,7 +120,8 @@ install:
 		$(DESTDIR)$(PREFIX)/bin/
 
 	# Install desktop files
-	install -m 644 data/*.desktop $(DESTDIR)$(PREFIX)/share/applications/
+	install -m 644 data/autostart/*.desktop $(DESTDIR)/etc/xdg/autostart/
+	install -m 644 data/*.desktop           $(DESTDIR)$(PREFIX)/share/applications/
 
 	# Install icons, 16x16
 	install -m 644 resources/16x16/cadence.png             $(DESTDIR)$(PREFIX)/share/icons/hicolor/16x16/apps/
@@ -188,9 +190,6 @@ install:
 		$(X11_RC_DIR)/70cadence-plugin-paths \
 		$(X11_RC_DIR)/99cadence-session-start
 
-	# get rid of some old files
-	rm -f $(DESTDIR)/etc/xdg/autostart/cadence-session-start.desktop
-
 # -----------------------------------------------------------------------------------------------------------------------------------------
 
 uninstall:

data/autostart/cadence-session-start.desktop

@@ -0,0 +1,11 @@
+[Desktop Entry]
+Encoding=UTF-8
+Version=1.0
+Type=Application
+Name=Cadence session startup
+Comment=Cadence session startup
+Exec=cadence-session-start --maybe-system-start
+Icon=cadence
+Terminal=false
+GenericName=
+NoDisplay=true

data/cadence-session-start

@@ -9,6 +9,7 @@ fi
 INSTALL_PREFIX="X-PREFIX-X"
 
 if [ "$1"x == "--system-start-by-x11-startup"x ]; then
+  # called via $STARTUP in 21cadence-session-inject
   $PYTHON $INSTALL_PREFIX/share/cadence/src/cadence_session_start.py --system-start &
   shift
   if [ "$1"x != ""x ]; then
@@ -16,6 +17,13 @@ if [ "$1"x == "--system-start-by-x11-startup"x ]; then
   else
     exec x-session-manager
   fi
+elif [ "$1"x == "--maybe-system-start"x ]; then
+  # called via autostart cadence-session-start.desktop
+  # only do something if 21cadence-session-inject was ignored
+  if [ "$CADENCE_AUTO_STARTED"x == ""x ]; then
+    exec $PYTHON $INSTALL_PREFIX/share/cadence/src/cadence_session_start.py --system-start
+  fi
 else
+  # called by user
   exec $PYTHON $INSTALL_PREFIX/share/cadence/src/cadence_session_start.py "$@"
 fi