sdk: PDBs fail to generate when referencing netstandard project from UWP app

Steps to reproduce

1. Create a solution with a UWP app and netstandard library using VS2017 RTW.
2. Reference the library from the UWP app.
3. Build an appx package in debug mode, or build an appxupload package, including symbol packages.

Results

The pdb files aren’t generated for the debug build or the appxupload. Release builds generate pdb files without apparent issue. Pdb files aren’t included in the appxupload package, even though the build succeeds.

This does not happen when referencing a PCL.

Update: MSBuild 15.1 gives the error Failed to convert FastLink symbols to full PDBs for '....pdb' due to failure to find the tool '\mspdbcmf.exe'.

Here is the diagnostic output from the msbuild task:

Target "_GenerateAppxSymbolPackage: (TargetId:237)" in file "C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets" from project "C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\App1.csproj" (target "_CreateAppxBundlePlatformSpecificArtifacts" depends on it):
Building target "_GenerateAppxSymbolPackage" completely.
Output file "C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\AppPackages\App1_1.1.7.0_Debug_Test\App1_1.1.7.0_x86_Debug.appxsym" does not exist.
Set Property: StripPrivateSymbols=false
Set Property: ReconstituteFastlinkPdbs=true
Set Property: MsPdbCmfExeFullpath=\mspdbcmf.exe
Using "GenerateAppxSymbolPackage" task from assembly "C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.Build.AppxPackage.dll".
Task "GenerateAppxSymbolPackage" (TaskId:488)
  Task Parameter:PdbCopyExeFullPath=C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\PDBCopy.exe (TaskId:488)
  Task Parameter:MsPdbCmfExeFullpath=\mspdbcmf.exe (TaskId:488)
  Task Parameter:
      PdbFiles=
          C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\bin\x86\Debug\App1.pdb
                  OutputGroup=DebugSymbolsProjectOutputGroup
                  ProjectName=App1
                  TargetPath=App1.pdb
          C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\ClassLibrary1\bin\Debug\netstandard1.4\ClassLibrary1.pdb
                  BuildReference=true
                  CopyLocal=true
                  FusionName=
                  MSBuildSourceProjectFile=C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\ClassLibrary1\ClassLibrary1.csproj
                  MSBuildSourceTargetName=Build
                  Name=ClassLibrary1
                  OriginalItemSpec=C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\ClassLibrary1\bin\Debug\netstandard1.4\ClassLibrary1.dll
                  OriginalProjectReferenceItemSpec=..\ClassLibrary1\ClassLibrary1.csproj
                  OutputGroup=CopyLocalFilesOutputGroup
                  OutputItemType=
                  Project={265dbec3-4830-48b8-88cc-6965bd5fec75}
                  ProjectName=App1
                  ReferenceOutputAssembly=true
                  ReferenceSourceTarget=ProjectReference
                  ResolvedFrom=C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\ClassLibrary1\bin\Debug\netstandard1.4\ClassLibrary1.dll
                  SetTargetFramework=TargetFramework=netstandard1.4;ProjectHasSingleTargetFramework=false;ProjectIsRidAgnostic=true
                  TargetPath=ClassLibrary1.pdb
                  Targets=
                  UndefineProperties=;ProjectHasSingleTargetFramework;RuntimeIdentifier;ProjectIsRidAgnostic
                  Version= (TaskId:488)
  Task Parameter:ProjectName=App1 (TaskId:488)
  Task Parameter:StrippedDirectory=obj\x86\Debug\Stripped (TaskId:488)
  Task Parameter:StripPrivateSymbols=False (TaskId:488)
  Task Parameter:ReconstituteFastlinkPdbs=True (TaskId:488)
  Task Parameter:AppxSymbolPackageOutput=C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\AppPackages\App1_1.1.7.0_Debug_Test\App1_1.1.7.0_x86_Debug.appxsym (TaskId:488)
  C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\PDBCopy.exe "C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\bin\x86\Debug\App1.pdb" obj\x86\Debug\Stripped\App1.pdb  (TaskId:488)
  Stripping private symbols from 'C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\bin\x86\Debug\App1.pdb'. (TaskId:488)
  C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\PDBCopy.exe "C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\ClassLibrary1\bin\Debug\netstandard1.4\ClassLibrary1.pdb" obj\x86\Debug\Stripped\ClassLibrary1.pdb  (TaskId:488)
  Can't open pdb file C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\ClassLibrary1\bin\Debug\netstandard1.4\ClassLibrary1.pdb (TaskId:488)
STRIPPRIVATESYMBOLS : error : EC_FILE_SYSTEM [C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\App1.csproj]
  The command exited with code 3. (TaskId:488)
C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\Microsoft\VisualStudio\v15.0\AppxPackage\Microsoft.AppXPackage.Targets(2670,5): error APPX0502: File '\mspdbcmf.exe' not found. [C:\Users\Develop\Documents\Visual Studio 2017\Projects\App1\App1\App1.csproj]
Done executing task "GenerateAppxSymbolPackage". (TaskId:488)

Workaround

In the .NET Standard project, set the DebugType to pdbonly e.g.:

<PropertyGroup>
    <DebugType>pdbonly</DebugType>
</PropertyGroup>

Or in the GUI, Project properties -> Build -> Advanced -> Debugging Information -> pdb-only

Issue also filed here.