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

[Jessica Clarke via llvm-commits]

jrtc27 wrote:

llvm-driver-template.cpp.in is what should be generating the real main for Clang (and call clang_main), and that was patched in this commit.

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