Allow access to a file in trace mode

[Ryan Schmidt]

If I try to build minivmac in trace mode (sudo port -t install minivmac) it fails because:

Warning: The following existing files were hidden from the build system by trace mode:
  /Applications/MacPorts/Mini vMac/vMac.ROM

The minivmac build requires access to this file. The file is not provided by any port; it must be provided by the user. How can I allow access to this file in trace mode in this port?