Do not sync VM time with clockvm if it's set to network time sync

When VM is set to synchronize the time with the network, to not sync its
time with clockvm.
Besides not having sense, in default configuration it will lead to
loopback qrexec connection (sys-net -> sys-net), which will hang.

QubesOS/qubes-issues#3333

Makefile

@@ -281,7 +281,8 @@ install-common: install-doc
 	install -m 0644 qubes-rpc/suspend-pre.README $(DESTDIR)/etc/qubes/suspend-pre.d/README
 	install -d $(DESTDIR)/etc/qubes/suspend-post.d
 	install -m 0644 qubes-rpc/suspend-post.README $(DESTDIR)/etc/qubes/suspend-post.d/README
-	ln -s $(BINDIR)/qvm-sync-clock $(DESTDIR)/etc/qubes/suspend-post.d/qvm-sync-clock.sh
+	install -m 0755 qubes-rpc/suspend-post-qvm-sync-clock.sh \
+		$(DESTDIR)/etc/qubes/suspend-post.d/qvm-sync-clock.sh
 	install -d $(DESTDIR)/etc/qubes/post-install.d
 	install -m 0644 post-install.d/README $(DESTDIR)/etc/qubes/post-install.d/
 	install -m 0755 post-install.d/*.sh $(DESTDIR)/etc/qubes/post-install.d/

qubes-rpc/suspend-post-qvm-sync-clock.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+if [ ! -f /var/run/qubes-service/clocksync ]; then
+    /usr/bin/qvm-sync-clock
+fi