Fix roslyn and nuget client output problems (#310)

* Define the order of GatherBuiltPackages and Package targets and fix output path for nuget-client.

* Remove "Build" from WriteVersions AfterTargets and fixup GatherBuiltPackages

Author: dseefeld

repos/dir.targets

@@ -166,7 +166,7 @@
   </Target>
 
   <Target Name="WriteVersions"
-          AfterTargets="Build;CopyPackage"
+          AfterTargets="CopyPackage"
           DependsOnTargets="GatherBuiltPackages">
     <WriteVersionsFile NugetPackages="@(_BuiltPackages)"
                        OutputPath="$(VersionFileLocation)"

repos/nuget-client.proj

@@ -2,7 +2,7 @@
 <Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), dir.props))/dir.props" />
   <PropertyGroup>
-    <PackagesOutput>$(ProjectDirectory)Nupkgs/</PackagesOutput>
+    <PackagesOutput>$(ProjectDirectory)artifacts/nupkgs/</PackagesOutput>
     <NuGetCoreSourceDirectory>$(ProjectDirectory)src/NuGet.Core/</NuGetCoreSourceDirectory>
     <ToolsDirectory>$(ProjectDirectory)cli/</ToolsDirectory>
     <NuGetKeyFilePath>$(KeysDir)NuGet.Client.snk</NuGetKeyFilePath>