[clang] Update stdckdint.h and make it available in pre-C23 modes. (PR #69649)

[via cfe-commits]

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@@ -1,12 +1,15 @@
 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 3
+// RUN: %clang_cc1 -triple=x86_64 -emit-llvm -verify -std=c99 %s -o - | FileCheck %s
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ZijunZhaoCCK wrote:

I don't add tests in clang/test/Headers/c11.c because I think here already covers and there are some specific flags/arguments in some of commands in c11.c.

https://github.com/llvm/llvm-project/pull/69649