Migration: [KNOWNISSUE] Mappings of multiple files to a single target file

[brthor]

filing this to track a known issue.

In project.json mapping multiple files to a single target file will cause nothing to be copied and no error to be thrown.

In MSBuild, the best we can achieve with the AssignTargetPaths mechanism is that the last file resolved is copied to the target path.

MSBuild discussion tracked here: dotnet/msbuild#989

[TheRealPiotrP]

This issue will be fixed in msbuild. There is nothing for migration to do here.