patch 9.0.0103: if running configure with cached results -lrt may be missing

Problem:    If running configure with cached results -lrt may be missing.
Solution:   Use two cache variables, one without and one with -lrt.
            (closes #10799)  Swap checks to avoid adding -lrt unnecessarily.

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    103,
 /**/
     102,
 /**/