[2962] Touch the dependency instead of using noop

If the cmdctl-certfile.pem is older than cmdctl-keyfile.pem for some
reason, make will try to run the rule every time.

src/bin/cmdctl/Makefile.am

@@ -60,15 +60,15 @@ b10_certgen_LDFLAGS = $(BOTAN_LIBS)
 cmdctl-keyfile.pem: b10-certgen
 	./b10-certgen -q -w
 
-# Do nothing. This is a hack, as b10-certgen creates both
-# cmdctl-keyfile.pem and cmdctl-certfile.pem, and in a parallel make,
-# making these targets simultaneously may result in corrupted
-# files. With GNU make, there is a non-portable way of working around
-# this with pattern rules, but we adopt this hack instead. The downside
-# is that cmdctl-certfile.pem will not be generated if
-# cmdctl-keyfile.pem exists. See Trac ticket #2962.
+# This is a hack, as b10-certgen creates both cmdctl-keyfile.pem and
+# cmdctl-certfile.pem, and in a parallel make, making these targets
+# simultaneously may result in corrupted files. With GNU make, there is
+# a non-portable way of working around this with pattern rules, but we
+# adopt this hack instead. The downside is that cmdctl-certfile.pem will
+# not be re-generated if cmdctl-keyfile.pem exists and is older. See
+# Trac ticket #2962.
 cmdctl-certfile.pem: cmdctl-keyfile.pem
-	noop
+	touch $(builddir)/cmdctl-keyfile.pem
 
 if INSTALL_CONFIGURATIONS