Localized assemblies are mistakenly flattened

[pharring]

Here's a repro. Note that System.Spatial includes localized resources for 9 languages.

1. Create a new .csproj with the following contents:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net45</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="System.Spatial" Version="5.8.2" />
  </ItemGroup>
</Project>

3. dotnet restore
4. dotnet build
5. Examine the bin\debug\net45

Result:
System.Spatial.resources.dll is alongside System.Spatial.dll
It's the zh-Hans version

Expect;
There should be 9 subfolders with the localized satellite DLLs.

Note: System.Spatial was chosen to demonstrate the issue. That nuget is commonly brought in via WindowsAzure.Storage

[pharring]

While the _CopyFilesMarkedCopyLocal correctly uses %(DestinationSubDirectory)%, it appears that property is being lost somewhere along the way.

From the build log, the target _HandlePackageFileConflicts produces a bunch of messages like;

Encountered conflict between 'CopyLocal:C:\Users\pharring.nuget\packages\system.spatial\5.8.2\lib\net40\de\System.Spatial.resources.dll' and
'CopyLocal:C:\Users\pharring.nuget\packages\system.spatial\5.8.2\lib\net40\es\System.Spatial.resources.dll'. Could not determine winner due to equal file and assembly versions.
[Emphasis mine]

[pharring]

Oh, seems to be a dupe of #1006