[llvm] [llvm-shlib] Fix parallel build failure in gen-msvc-exports.py on Windows (PR #197190)

[Jinsong Ji via llvm-commits]

jsji wrote:

> I wasn't able to find anything about necessity to have the file in https://reviews.llvm.org/D35077. Tagging @Wallbraker just in case.
> 
> I don't see anything critical. Maybe the only concern is about quite long `nm` output. But I don't think that it is a real problem.
> 
> LGTM

Thanks @e-kud .

https://github.com/llvm/llvm-project/pull/197190