[clang] [llvm] [RISCV] Add Spacemit X100 processor definition (PR #173988)

[Mark Zhuang via cfe-commits]

zqb-all wrote:

> > Hi @topperc , the web page mentions: `"After your PR is reviewed and accepted, you want to rebase your branch to ensure you won’t encounter merge conflicts when landing the PR."` Should I now rebase locally, then force push, and finally merge?
> 
> I'm not sure why that says "rebase". A merge commit with `main` should be fine. The PR will be squashed anyway.

Got it. No need to rebase manually. Thanks.

https://github.com/llvm/llvm-project/pull/173988