[llvm] [Support] Check zstd decompress result before msan unpoison (PR #117276)

[Wu Yingcong via llvm-commits]

yingcong-wu wrote:

For the CI failure, I think the test result looks good, the problem seems to be with 
```
python3 /var/lib/buildkite-agent/builds/linux-56-59b8f5d88-mqg5l-1/llvm-project/github-pull-requests/.ci/generate_test_report.py
```

Does it count as an infrastructure problem?

https://github.com/llvm/llvm-project/pull/117276