Add messages to ease debugging

nit: Shorten 'NuGet.exe restore' command lines slightly

Author: dougbu

Runtime.msbuild

@@ -84,18 +84,23 @@
 
     <!-- Need three phases to build correctly due to dependencies between legacy and SDK-style projects -->
     <!-- 1. Special case NetCore project because an SDK test project depends on it. -->
+    <Message Importance="High" Text='%0A&gt; "$(NuGetExe)" restore "src\System.Net.Http.Formatting.NetCore\packages.config" ...'
+      Condition=" '$(BuildPortable)' == 'true' " />
     <Exec Command='"$(NuGetExe)" restore "src\System.Net.Http.Formatting.NetCore\packages.config" ^
         -PackagesDirectory packages -NonInteractive ^
-        -Verbosity quiet -ConfigFile "$(MSBuildThisFileDirectory)\.nuget\NuGet.Config"'
+        -Verbosity quiet -ConfigFile .nuget\NuGet.Config'
       Condition=" '$(BuildPortable)' == 'true' " />
     <!-- 2. Restore SDK-style test projects because legacy test projects depend on TestCommon. -->
+    <Message Importance="High" Text='%0A&gt; dotnet restore "@(_ProjectsToRestore)"' />
     <MSBuild Projects="@(_ProjectsToRestore)" Targets="Restore"
       BuildInParallel="$(BuildInParallel)"
       Properties="Configuration=$(Configuration);CodeAnalysis=$(CodeAnalysis);StyleCopEnabled=$(StyleCopEnabled);VisualStudioVersion=$(VisualStudioVersion)" />
     <!-- 3. Restore remaining legacy projects. -->
+    <Message Importance="High" Text='%0A&gt; "$(NuGetExe)" restore "@(_NuGetPackagesAndSolutions)" ...' />
     <Exec Command='"$(NuGetExe)" restore "%(_NuGetPackagesAndSolutions.Identity)" ^
         -PackagesDirectory packages -NonInteractive ^
-        -Verbosity quiet -ConfigFile "$(MSBuildThisFileDirectory)\.nuget\NuGet.Config"' />
+        -Verbosity quiet -ConfigFile .nuget\NuGet.Config' />
+    <Message Importance="High" Text='' />
   </Target>
 
   <!-- Pick the right Microsoft.Web.FxCop package to use and copy it to a standard location. -->