Keep setuid bit for weston-launch

dh_fixperms nowadays strips this, but weston-launch needs it.

Cherry-picked from:
https://salsa.debian.org/xorg-team/wayland/weston/blob/weston-5.0.0-3/debian/rules

Change-Id: Iec46a9cbe5fd0010802e0b05660d01bae3a6125f
diff --git a/debian/rules b/debian/rules
index e74a8cc..e08f087 100755
--- a/debian/rules
+++ b/debian/rules
@@ -8,3 +8,6 @@
 
 override_dh_auto_test:
 	true
+
+override_dh_fixperms:
+	dh_fixperms -Xusr/bin/weston-launch