Update build to support expanding target files to by signed by TFM

after.mstestex.sln.targets

@@ -7,7 +7,7 @@
 
     <PropertyGroup>
       <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
-      <BuildProperties>Configuration=$(Configuration)</BuildProperties>
+      <BuildProperties>Configuration=$(Configuration);TargetFramework=netstandard1.0</BuildProperties>
       <BuildProperties Condition=" ('$(Platform)' != '') AND ('$(Platform)' != 'AnyCPU') AND ('$(Platform)' != 'Any CPU') ">$(BuildProperties);Platform=$(Platform)</BuildProperties>
     </PropertyGroup>
 
@@ -22,7 +22,7 @@
     <PropertyGroup>
       <!-- transform list to pipe-separated values so we can forward it as a parameter using a build property -->
       <SigningProperties>
-        SourceDir=$(MSBuildThisFileDirectory)\src;
+        SourceDir=$(MSBuildThisFileDirectory)src\;
         FilesToSign=@(TargetFiles->'%(Identity)','|')
       </SigningProperties>
     </PropertyGroup>

src/directory.build.targets

@@ -7,6 +7,26 @@
     <Import Project="..\build\nuget.targets" />
   </ImportGroup>
 
-  <Target Name="GetTargetPath" Outputs="$(TargetPath)" />
+  <Target Name="GetTargetPath" Outputs="@(TargetPath)">
+
+    <PropertyGroup>
+      <TargetFrameworks Condition=" '$(TargetFrameworks)' == '' ">$(TargetFramework)</TargetFrameworks>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <_TargetFrameworks Include="$(TargetFrameworks)" />
+    </ItemGroup>
+
+    <MSBuild Projects="$(MSBuildProjectFullPath)"
+             Targets="GetTargetPathForTfm"
+             Properties="Configuration=$(Configuration);TargetFramework=%(_TargetFrameworks.Identity)"
+             UnloadProjectsOnCompletion="true"
+             BuildInParallel="true">
+      <Output TaskParameter="TargetOutputs" ItemName="TargetPath" />
+    </MSBuild>
+
+  </Target>
+
+  <Target Name="GetTargetPathForTfm" Outputs="$(TargetPath)" />
 
 </Project>