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

[Mark Zhuang via cfe-commits]

zqb-all wrote:

> Please do not force push in PRs without a good reason. https://llvm.org/docs/GitHub.html#rebasing-pull-requests-and-force-pushes

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?

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