Regression: Pack targets failing - trying to add pdb for embedded type

_From @onovotny on November 28, 2017 1:48_

I’m seeing a regression that’s causing Ix.NET to fail with 2.0.3 and higher. I don’t know when the break was introduced. Nothing in Ix has changed related to this:
https://github.com/Reactive-Extensions/Rx.NET/tree/develop/Ix.NET/Source

Getting errors like this:
"C:\dev\RxNET\Ix.NET\Source\System.Interactive\System.Interactive.csproj" (pack target) (1) ->
(GenerateNuspec target) ->
C:\Program Files\dotnet\sdk\2.1.1-preview-007165\Sdks\NuGet.Build.Tasks.Pack\buildCrossTargeting\NuGet.Build.Tasks.Pack.targets(204,5): err or : The file 'C:\dev\RxNET\Ix.NET\Source\System.Interactive\bin\Release\net45\System.Interactive.pdb' to be packed was not found on disk. [C :\dev\RxNET\Ix.NET\Source\System.Interactive\System.Interactive.csproj]

And the build log shows this:

This is in error because there are no symbols for DebugType = embedded. The build log clearly shows DebugType set to embedded.

[msbuild.zip](https://github.com/NuGet/Home/files/1508255/msbuild.zip)

_Copied from original issue: NuGet/Home#6230_

Reproduce the pack target failure from Ix.NET/Source, starting with System.Interactive/System.Interactive.csproj and the NuGet.Build.Tasks.Pack buildCrossTargeting target at line 204. Use the attached msbuild.zip log to compare DebugType=embedded with the requested PDB; done means the pack target no longer fails because the expected net45 PDB is missing.

Written by the indexing model from the issue text.