maint: ensure dd's computation of O_FULLBLOCK uses all O_ symbol names

* src/dd.c (O_FULLBLOCK): Use a more uniform initializer, that makes
it easier to extract all O_ symbol names.
* maint.mk (syntax-check-rules): Also search for sc_ rules in cfg.mk.
(sc_root_tests): Ensure that this rule sets $diff.
* cfg.mk (sc_dd_O_FLAGS): New rule.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/dd.c b/src/dd.c
index 763961261..d683c5d67 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -279,7 +279,8 @@ enum
 		    MAX (O_NOFOLLOW,
 		    MAX (O_NOLINKS,
 		    MAX (O_NONBLOCK,
-		    MAX (O_SYNC, O_TEXT))))))))))))) << 1)
+		    MAX (O_SYNC,
+		    MAX (O_TEXT, 0)))))))))))))) << 1)
   };
 
 /* Ensure that we didn't shift it off the end.  */