patch 8.1.2239: CI fails when running tests without building Vim

Problem:    CI fails when running tests without building Vim.
Solution:   Skip creating doc tags if the execute does not exist.

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2239,
 /**/
     2238,
 /**/