BUG/BUILD: replace haproxy-systemd-wrapper with $(EXTRA) in install-bin.

[wt: this should be backported to 1.6 and 1.5 as well since some platforms
 don't build the systemd-wrapper]
(cherry picked from commit 796d2fc136359c31c5c35f00c0751890ab42a016)
(cherry picked from commit 9d0b47d96825b0584ea81c826a96ed8babcc016b)
diff --git a/Makefile b/Makefile
index 9556069..e3199b2 100644
--- a/Makefile
+++ b/Makefile
@@ -719,10 +719,9 @@
 		install -m 644 doc/$$x.txt "$(DESTDIR)$(DOCDIR)" ; \
 	done
 
-install-bin: haproxy haproxy-systemd-wrapper
+install-bin: haproxy $(EXTRA)
 	install -d "$(DESTDIR)$(SBINDIR)"
-	install haproxy "$(DESTDIR)$(SBINDIR)"
-	install haproxy-systemd-wrapper "$(DESTDIR)$(SBINDIR)"
+	install haproxy $(EXTRA) "$(DESTDIR)$(SBINDIR)"
 
 install: install-bin install-man install-doc