[llvm] [llvm-ml] Fix RIP-relative addressing for ptr operands (PR #107618)

[Andrew Ng via llvm-commits]

nga888 wrote:

> Have we confirmed that this fully fixes #54773 ?
> 
> I'm prepared to approve this if so - it seems to match ml64's behavior - but I don't want us closing the other bug if this doesn't fix it!

I have checked that using `llvm-ml.exe` with this patch applied to the LLVM 18 toolchain can build a Windows x64 LLVM 19 toolchain that runs and doesn't crash because of the mis-assembly of the Blake3 MASM assembly source.

It was my own experiment of trying to replace MS `ml64.exe` with `llvm-ml.exe -m64` in my Windows build that led me to this issue...

https://github.com/llvm/llvm-project/pull/107618