A couple of open flags used in an assertion didn't exist in macOS 10.4.
Per build farm animal prairiedog. Also add O_EXCL while here (there are
a few more standard flags but they're not relevant and likely to be
missing).
*/
StaticAssertStmt((PG_O_DIRECT &
(O_APPEND |
+#if defined(O_CLOEXEC)
O_CLOEXEC |
+#endif
O_CREAT |
+#if defined(O_DSYNC)
O_DSYNC |
+#endif
+ O_EXCL |
O_RDWR |
O_RDONLY |
O_SYNC |