[docs] HowToSubmitABug update?

Hi Jan,

From what I understand, except https://llvm.org/docs/HowToSubmitABug.html#incorrect-code-generation , the rest of https://llvm.org/docs/HowToSubmitABug.html seems fine. C backend is removed from the code base, and I don’t know what is the proper way to debug incorrect code generation.

Since you mentioned clang crash, I think you can tell the clang user start with https://llvm.org/docs/HowToSubmitABug.html#crashing-bugs to figure out if it’s clang or llvm bug.