Skip non-dll files when reading PE metadata
Fix "kpm build" output

- Use better format with coloring
- Fix a bug when building with unresolved dependencies
Apply similar format to "kpm pack" output
Modify build script to pick latest CoreCLR package

On the CI this would cause the build to pick up the package from the
volatile feed.
Reacting to System.Collections.Concurrent versioning change
Use non-recursive copy operation to fix path too long exception during "kpm pack"