[clang] [clang][RISCV] Support `norelax` attribute for RISCV (PR #115981)

[Yangyu Chen via cfe-commits]

cyyself wrote:

> Two comments:
> 
> * I don't think the c-api-doc change is going to be accepted at this rate

I agree. I also changed my mind now through the discussion from the c-api-doc PR.


https://github.com/llvm/llvm-project/pull/115981