build: allow 'make syntax-check' on fresh checkout

For good or for bad, I did a fresh checkout, ./autogen.sh, then
'configure', then 'make syntax-check', and was surprised that it
failed.  Running 'make' before 'make syntax-check' cleaned up the
issue, but this patch makes it work up front.

* cfg.mk (sc_po_check): Add prerequisites.

cfg.mk

@@ -605,6 +605,14 @@ _autogen:
 # regenerate HACKING as part of the syntax-check
 syntax-check: $(top_srcdir)/HACKING
 
+# sc_po_check can fail if generated files are not built first
+sc_po_check: $(srcdir)/daemon/remote_dispatch.h \
+		$(srcdir)/src/remote/remote_client_bodies.h
+$(srcdir)/daemon/remote_dispatch.h:
+	$(MAKE) -C daemon remote_dispatch.h
+$(srcdir)/src/remote/remote_client_bodies.h:
+	$(MAKE) -C src remote/remote_client_bodies.h
+
 # List all syntax-check exemptions:
 exclude_file_name_regexp--sc_avoid_strcase = ^tools/virsh\.c$$