[llvm] [llvm-shlib] Fix the version naming style of libLLVM for Windows (PR #85710)

[Christoph Reiter via llvm-commits]

lazka wrote:

Thanks. Note that it's `libLLVM-18.1.dll` in MSYS2 atm since we pached it differently to align with unix (major.minor being the new ABI version)

https://github.com/llvm/llvm-project/pull/85710