The legacy Visual Studio solution is currently the only way to still
build the legacy D3D8 and D3D9 libraries. Make sure they build
correctly so we can put it in a branch before deleting it from master.

Bug: b/139189696
Change-Id: Ibb1625c28561e2d7d323890c4b872acb9c153804
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/43229Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>