[clang-tools-extra] Add new tool: clang-read-diagnostics (PR #118522)

[Yuxuan Chen via cfe-commits]

yuxuanchen1997 wrote:

> I'd like to understand the motivation for the tool a bit better. IMO, the goal should be to deprecate serialized diagnostics because we are now able to emit diagnostics to SARIF instead, and the whole point to SARIF is to be a machine-readable interchange format for diagnostic information to be shared between tools. So if we want to promote SARIF for sharing diagnostics between tools, it seems like we don't really need a tool to deserialized diagnostics we've serialized.
> 
> CC @cjdb for awareness, as he's been working on SARIF support.

The goal of these tools is to eventually be able to obtain clang diagnostics as structural data. Say, I want the compiler to emit warnings and learn about the number of warnings I will get. I didn't know that we plan to deprecate serialized diagnostics. I would have done differently if I had known about SARIF.

https://github.com/llvm/llvm-project/pull/118522