Explicitly use NuGet.Config for additional sources

Author: kzu

build.proj

@@ -74,8 +74,8 @@
 	</Target>
 
 	<Target Name="Restore">
-		<Exec Command='"$(NuGet)" Restore "%(Solution.FullPath)" -Verbosity quiet' />
-		<Exec Command='"$(NuGet)" Restore "src\VisualStudio\NuGet.Packaging.VisualStudio.sln" -Verbosity quiet' />
+		<Exec Command='"$(NuGet)" Restore "%(Solution.FullPath)" -Verbosity quiet -Config src\NuGet.Config' />
+		<Exec Command='"$(NuGet)" Restore "src\VisualStudio\NuGet.Packaging.VisualStudio.sln" -Verbosity quiet -Config src\NuGet.Config' />
 	</Target>
 
 	<Target Name="Coverage" DependsOnTargets="Build">

src/NuGet.Config

@@ -2,7 +2,7 @@
 <configuration>
 	<packageSources>
 		<clear />
-    <add key="NuGetCI" value="https://dotnet.myget.org/F/nuget-build/api/v3/index.json" />
+		<add key="NuGetCI" value="https://dotnet.myget.org/F/nuget-build/api/v3/index.json" />
 		<add key="NuGet.org" value="https://api.nuget.org/v3/index.json" />
 		<add key="Merq-CI" value="https://ci.appveyor.com/nuget/merq" />
 		<add key="Clide-CI" value="https://ci.appveyor.com/nuget/clide" />