Acr build vague error when using symbolic links

[rosanch]

Describe the bug When having a symbolic link in the working directory that file, build fails to untar the symbolic link file but outputs failed to download source instead.

To Reproduce Steps to reproduce the behavior:

1. create a symbolic link pointing to a resource outside your workspace.
2. run build from that workspace.

Expected behavior Should output invalid symlink "/workspace/etc -> /something