[llvm] [llvm][Docs] Fix incorrect command linking compile_commands.json (PR #123412)

[Carlo Cabrera via llvm-commits]

https://github.com/carlocab commented:

I think this command assumes you are running from inside the `build` directory:

https://github.com/llvm/llvm-project/blob/main/llvm/docs/MyFirstTypoFix.rst#L117

https://github.com/llvm/llvm-project/pull/123412