patch 8.1.0509: checking cwd not accessible fails for root

Problem:    Checking cwd not accessible fails for root. (James McCoy)
Solution:   Skip this part of the test for root. (closes #3595)

src/version.c

@@ -792,6 +792,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    509,
 /**/
     508,
 /**/