moved checksum_builder/libchechsum to top srcdir to respect build order

src/Makefile.am

@@ -44,6 +44,10 @@ if USE_MEDSRV
   SUBDIRS += medsrv
 endif
 
+if USE_INTEGRITY_TEST
+  SUBDIRS += checksum
+endif
+
 EXTRA_DIST = strongswan.conf
 
 install-exec-local :	

src/libstrongswan/Makefile.am

@@ -197,7 +197,3 @@ endif
 if USE_TEST_VECTORS
   SUBDIRS += plugins/test_vectors
 endif
-
-if USE_INTEGRITY_TEST
-  SUBDIRS += checksum
-endif