This reverts commit 87c408b42d.
CL.exe doesn't seem to be in the path any more when using the
AppVeyor Visual Studio 2017 environment.
msbuild "C:\projects\libsodium\libsodium.vcxproj" /m /verbosity:minimal /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll"
Microsoft (R) Build Engine version 15.1.548.43366
Copyright (C) Microsoft Corporation. All rights reserved.
TRACKER : error TRK0005: Failed to locate: "CL.exe". The system cannot find the file specified. [C:\projects\libsodium\libsodium.vcxproj]