[clang] [lld] [llvm] [llvm-driver] Fix usage of `InitLLVM` on Windows (PR #76306)

[Dimitry Andric via cfe-commits]

DimitryAndric wrote:

Ah that was my error, I hadn't used the regenerated `*-driver.cpp` files. These indeed should contain the `InitLLVM` call.

https://github.com/llvm/llvm-project/pull/76306