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)
diff --git a/src/version.c b/src/version.c
index 395db11..e9c65bc 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2175,
+/**/
     2174,
 /**/
     2173,