[clang] [lldb] [llvm] [Support][Driver][LLDB] Guard WIN32_LEAN_AND_MEAN definitions with #ifndef (PR #213045)

[David Young via cfe-commits]

youngd007 wrote:

See the various minmax ifdef guards
https://github.com/search?q=repo%3Allvm%2Fllvm-project%20%23ifndef%20NOMINMAX&type=code

https://github.com/llvm/llvm-project/pull/213045