Makefile.am: Avoid include/ depending on lib/.

Add a build check that public openvswitch header file should not include
internal library.

Suggested-by: Joe Stringer <joe@ovn.org>
Suggested-by: Daniele Di Proietto <diproiettod@vmware.com>
Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: Joe Stringer <joe@ovn.org>

Makefile.am

@@ -230,6 +230,13 @@ config-h-check:
 	  echo "every C source file must #include <config.h>."; \
 	  exit 1; \
 	fi
+	if grep '#include' $(srcdir)/include/openvswitch/*.h | \
+	    grep -vE '(<.*>)|("openvswitch)|("openflow)'; \
+	then \
+	  echo "See above for list of violations of the rule that"; \
+	  echo "public openvswitch header file should not include internal library."; \
+	  exit 1; \
+	fi
 .PHONY: config-h-check
 
 # Check for printf() type modifiers that MSVC doesn't support.