Update GitVersionBuild.targets

Added _GetOutputItemsFromPack to GetVersion target's BeforeTargets items.
It fixes issue #1604

Author: Mephistofeles

src/GitVersionTask/NugetAssets/build/functionality/GitVersionBuild.targets

@@ -42,7 +42,7 @@
     </ItemGroup>
   </Target>
 
-  <Target Name="GetVersion" BeforeTargets="CoreCompile;GetAssemblyVersion;GenerateNuspec;_GenerateRestoreProjectSpec;EnsureWixToolsetInstalled" Condition="$(GetVersion) == 'true'">
+  <Target Name="GetVersion" BeforeTargets="CoreCompile;GetAssemblyVersion;GenerateNuspec;_GenerateRestoreProjectSpec;_GetOutputItemsFromPack;EnsureWixToolsetInstalled" Condition="$(GetVersion) == 'true'">
 
     <GetVersion SolutionDirectory="$(GitVersionPath)" NoFetch="$(GitVersion_NoFetchEnabled)">
       <Output TaskParameter="Major" PropertyName="GitVersion_Major" />