[master] Update dependencies from dotnet/arcade (#2667)

* Update dependencies from https://github.com/dotnet/arcade build 20190626.44

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19326.44

* Add missing feed

* Use PackageDownload

* Update dependencies from https://github.com/dotnet/arcade build 20190627.39

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19327.39

* Use new apphost package and stop downloading extra packages

eng/common/post-build/nuget-validation.ps1

@@ -0,0 +1,28 @@
+# This script validates NuGet package metadata information using this 
+# tool: https://github.com/NuGet/NuGetGallery/tree/jver-verify/src/VerifyMicrosoftPackage
+
+param(
+  [Parameter(Mandatory=$true)][string] $PackagesPath,           # Path to where the packages to be validated are
+  [Parameter(Mandatory=$true)][string] $ToolDestinationPath     # Where the validation tool should be downloaded to
+)
+
+$ErrorActionPreference = "Stop"
+Set-StrictMode -Version 2.0
+
+. $PSScriptRoot\..\tools.ps1
+
+try {
+  $url = "https://raw.githubusercontent.com/NuGet/NuGetGallery/jver-verify/src/VerifyMicrosoftPackage/verify.ps1" 
+
+  New-Item -ItemType "directory" -Path ${ToolDestinationPath} -Force
+
+  Invoke-WebRequest $url -OutFile ${ToolDestinationPath}\verify.ps1 
+
+  & ${ToolDestinationPath}\verify.ps1 ${PackagesPath}\*.nupkg
+} 
+catch {
+  Write-PipelineTaskError "NuGet package validation failed. Please check error logs."
+  Write-Host $_
+  Write-Host $_.ScriptStackTrace
+  ExitWithExitCode 1
+}