[llvm] added a script to update llvm-mc test file (PR #107246)

[Brox Chen via llvm-commits]

broxigarchen wrote:

> Nice idea.
> 
> Does this work for combined asm/disasm tests, e.g., `gfx12_asm_vop1.s`? Does this work for other backend's asm/disasm tests?

I tried gfx12_asm_vop1.s, but seems the script does not understand the %extract_encoding% in the cmd line. I think it requires some parsing for these special tokens.

Regarding to the other backend, I did a quick look, and it seems some tests are using ".section" as test seperators so there must be lot of cases that are not covered.

https://github.com/llvm/llvm-project/pull/107246