Build with latest SDK

Rx.NET/Source/System.Reactive.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 15
-VisualStudioVersion = 15.0.26606.0
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.28606.126
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "System.Reactive", "src\System.Reactive\System.Reactive.csproj", "{01706A0F-8A63-4FD6-AF45-0BC0BED3C0D9}"
 EndProject
@@ -15,9 +15,7 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Tests.System.Reactive.Uwp.D
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{870348D0-C0A0-4352-8A02-E00AB0CCB919}"
 	ProjectSection(SolutionItems) = preProject
-		..\..\.vsts.rx-ci.yml = ..\..\.vsts.rx-ci.yml
-		..\..\.vsts.rx-pr.yml = ..\..\.vsts.rx-pr.yml
-		..\..\.vsts.rx-shared.yml = ..\..\.vsts.rx-shared.yml
+		..\..\azure-pipelines.rx.yml = ..\..\azure-pipelines.rx.yml
 		Directory.build.props = Directory.build.props
 		Directory.build.targets = Directory.build.targets
 		global.json = global.json

azure-pipelines.rx.yml

@@ -29,6 +29,10 @@ steps:
   displayName: Set Version
   condition: and(succeeded(), eq(variables['system.pullrequest.isfork'], false))
 
+- task: DotNetCoreInstaller@0
+  inputs:
+    version: '2.2.104'
+
 - task: MSBuild@1
   displayName: Build System.Reactive.sln
   inputs:
@@ -45,15 +49,6 @@ steps:
     arguments: pack Rx.NET/Source/facades/System.Reactive.Compatibility.nuspec -Version $(NBGV_NuGetPackageVersion) -MinClientVersion 2.12 -NoPackageAnalysis -outputdirectory $(Build.ArtifactStagingDirectory)\artifacts
   condition: eq(variables['system.pullrequest.isfork'], false)
 
-- task: MSBuild@1
-  displayName: Build for Test (ppdb) workaround
-  inputs:
-    solution: Rx.NET/Source/System.Reactive.sln    
-    msbuildArguments: /t:build /p:DebugType=portable
-    platform: $(BuildPlatform)
-    configuration: $(BuildConfiguration)
-    maximumCpuCount: true
-
 - task: DotNetCoreCLI@2
   inputs:
     command: test