Produce a Visual Studio error for unreferenced local variables
Produce a Visual Studio error for unreferenced local variables

This is already a warning which gets treated as an error when compiling
with Clang [-Werror=unused-variable]

Bug: b/130335507
Change-Id: Id500ab51e11e4e77553af4f8a5f556663dcd5852
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/59450
Kokoro-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Tested-by: Nicolas Capens <51edc787c30f24c4904e8ffbb5523c3a9f7a451d@google.com>
Reviewed-by: Alexis Hétu <1c7141772178a7e80858c3db5052b328076f08f4@google.com>

google/swiftshader,google/swiftshader,google/swiftshader