CMake's CMAKE_BUILD_TYPE variable is ignored for multi-config
generators,like Visual Studio. Instead, we must specify the config when
building.

For VulkanTester, needed to add "RelWithDebInfo" to search paths for
vk_swiftshader.dll as that's the "Release" config we use for Kokoro
builds.

Change-Id: I1fbfa3b179e9364462f4ea6e9704120d3a675b4d
Bug: b/181019484
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/53188
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Kokoro-Result: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>