patch 8.2.2175: github actions: clang-11 handling suboptimal

Problem:    Github actions: clang-11 handling suboptimal.
Solution:   Separate step of installing clang-11. Get ubuntu release name
            dynamically. (Ozaki Kiichi, closes #7514)

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2175,
 /**/
     2174,
 /**/