Only copy devkit assemblies when doing a real build

Author: dibarbet

src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/Microsoft.CodeAnalysis.LanguageServer.UnitTests.csproj

@@ -38,3 +38,4 @@
     </ItemGroup>
   </Target>
 </Project>
+

src/VisualStudio/DevKit/Impl/Microsoft.VisualStudio.LanguageServices.DevKit.csproj

@@ -55,8 +55,11 @@
     <Content Include="$(TargetPath)" Pack="true" PackagePath="content" CopyToOutputDirectory="PreserveNewest" />
   </ItemGroup>
 
-  <!-- Used by LanguageServer.UnitTests project to be able to copy all the content to its own directory -->
-  <Target Name="GetPackInputs" DependsOnTargets="Build" Returns="@(_Content)">
+  <!--
+    Used by LanguageServer.UnitTests project to be able to copy all the content to its own directory.
+    Only needs to run as part of a real build, so skip it in design time builds to prevent issues.
+  -->
+  <Target Name="GetPackInputs" DependsOnTargets="Build" Returns="@(_Content)" Condition="'$(DesignTimeBuild)' != 'true'">
     <ItemGroup>
       <_Content Include="@(Content)" Condition="'%(Content.Pack)'=='true'"/>
     </ItemGroup>