[clang] [clang] Catch missing format attributes (PR #70024)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-darwin` running on `doug-worker-3` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/23/builds/925

Here is the relevant piece of the build log for the reference:
```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: Sema/attr-format-missing.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/clang -cc1 -internal-isystem /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/lib/clang/19/include -nostdsysteminc -fsyntax-only -verify=expected,c_diagnostics -Wmissing-format-attribute /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Sema/attr-format-missing.c
+ /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/bin/clang -cc1 -internal-isystem /Volumes/RAMDisk/buildbot-root/x86_64-darwin/build/lib/clang/19/include -nostdsysteminc -fsyntax-only -verify=expected,c_diagnostics -Wmissing-format-attribute /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Sema/attr-format-missing.c
error: 'c_diagnostics-warning' diagnostics seen but not expected: 
  File /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Sema/attr-format-missing.c Line 391: incompatible pointer types passing 'char *' to parameter of type 'struct __va_list_tag *'
error: 'c_diagnostics-note' diagnostics seen but not expected: 
  File /Volumes/RAMDisk/buildbot-root/x86_64-darwin/llvm-project/clang/test/Sema/attr-format-missing.c Line 30: passing argument to parameter here
2 errors generated.

--

********************


```

https://github.com/llvm/llvm-project/pull/70024