patch 9.1.1729: CI is not run with clang 21

Problem:  CI is not run with clang 21
Solution: Update CI to v21, fix a few warnings that are uncovered when
          using clang 21 (Philip H)

closes: #18142

Signed-off-by: Philip H. <47042125+pheiduck@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
     env:
       CC: ${{ matrix.compiler }}
       GCC_VER: 14
-      CLANG_VER: 20
+      CLANG_VER: 21
       TEST: test
       SRCDIR: ./src
       LEAK_CFLAGS: -DEXITFREE

src/if_ruby.c

@@ -107,15 +107,21 @@
 # undef SIZEOF_TIME_T
 #endif
 
-#ifdef __GNUC__
+#if defined(__GNUC__) || defined(__clang__)
 # pragma GCC diagnostic push
 # pragma GCC diagnostic ignored "-Wunused-parameter"
 #endif
+
+#if defined(__clang__) && (__clang_major__ >= 21)
+# pragma GCC diagnostic ignored "-Wdefault-const-init-field-unsafe"
+#endif
+
 #include <ruby.h>
-#ifdef __GNUC__
+#include <ruby/encoding.h>
+
+#if defined(__GNUC__) || defined(__clang__)
 # pragma GCC diagnostic pop
 #endif
-#include <ruby/encoding.h>
 
 // See above.
 #ifdef SIZEOF_TIME_T

src/version.c

@@ -724,6 +724,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1729,
 /**/
     1728,
 /**/