[cmake] Remove MSVC C4180 override
[cmake] Remove MSVC C4180 override

Tested on VS2017 and VS2019 llvm/clang builds with WX enabled - its no longer necessary to disable this warning.

Differential Revision: https://reviews.llvm.org/D67103

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@370871 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm