libmpathutil: avoid -Wcast-function-type-mismatch error with clang 19

Avoid the following error with clang 19:

msort.c:268:27: error: cast from '__compar_fn_t' (aka 'int (*)(const void *, const void *)') to '__compar_d_fn_t' (aka 'int (*)(const void *, const void *, void *)') converts to incompatible function type [-Werror,-Wcast-function-type-mismatch]
  268 |         return msort_r (b, n, s, (__compar_d_fn_t)cmp, NULL);
      |                                  ^~~~~~~~~~~~~~~~~~~~

Signed-off-by: Martin Wilck <[email protected]>

libmpathutil/msort.c

@@ -259,9 +259,12 @@ msort_r (void *b, size_t n, size_t s, __compar_d_fn_t cmp, void *arg)
  * If this is safe for them, it should be for us, too.
  */
 #pragma GCC diagnostic push
-#if __GNUC__ >= 8
+#if __GNUC__ >= 8 || __clang_major__ >= 19
 #pragma GCC diagnostic ignored "-Wcast-function-type"
 #endif
+#if __clang_major__ >= 19
+#pragma GCC diagnostic ignored "-Wcast-function-type-mismatch"
+#endif
 void
 msort (void *b, size_t n, size_t s, __compar_fn_t cmp)
 {