Restoring with invalid target framework says 'unsupported' instead of showing bad framework name #5413
Description
Given <TargetFramework>abc123</TargetFramework>, RestoreTask yields:
C:\Program Files (x86)\Microsoft Visual Studio\Preview\Enterprise\Common7\IDE\CommonExtensions\Microsoft\NuGet\NuGet.targets(102,5):
error : Invalid restore input. Invalid target framework 'unsupported'. Input files: D:\Temp\qwerty\qwerty.csproj. [D:\Temp\qwerty\qwerty.csproj]
It should indicate the badly spelled framework 'abc13' in the error message instead of 'unsupported'.
We tried to fix this by running our own check before restore in the SDK, but that breaks adding support for additional TFMs like uap using the MSBuild.Sdk.Extras package.