Added WINDOWS constant for MSBuild

Author: Pyrdacor

FreeserfNet.sln

@@ -15,6 +15,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		.gitignore = .gitignore
 		.travis.yml = .travis.yml
 		appveyor.yml = appveyor.yml
+		azure-pipelines.yml = azure-pipelines.yml
 		changelog.txt = changelog.txt
 		LICENSE = LICENSE
 		linux_build = linux_build
@@ -27,7 +28,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Silk.NET.Window", "Silk.NET
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Freeserf.Test", "Freeserf.Test\Freeserf.Test.csproj", "{B2FEC47F-6033-43EC-A1F4-B5D5983CBB8E}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Freeserf.Audio", "Freeserf.Audio\Freeserf.Audio.csproj", "{E7355C62-2C99-48CF-99C9-40AE9EC9886F}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Freeserf.Audio", "Freeserf.Audio\Freeserf.Audio.csproj", "{E7355C62-2C99-48CF-99C9-40AE9EC9886F}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution

azure-pipelines.yml

@@ -1,8 +1,3 @@
-# .NET Desktop
-# Build and run tests for .NET Desktop or Windows classic desktop solutions.
-# Add steps that publish symbols, save build artifacts, and more:
-# https://docs.microsoft.com/azure/devops/pipelines/apps/windows/dot-net
-
 trigger:
 - master
 
@@ -26,6 +21,7 @@ steps:
     solution: '$(solution)'
     platform: '$(buildPlatform)'
     configuration: '$(buildConfiguration)'
+    msbuildArguments: '/p:DefineConstants=WINDOWS'
 
 - task: VSTest@2
   inputs: