I am able to reproduce the failure if the apple-gcc42 port is installed with the bootstrap variant and the cctools and ld64 ports are not installed.
I am not able to reproduce the failure if the apple-gcc42 port is installed without the bootstrap variant; deselecting this variant brings in cctools and ld64 as dependencies.
So the immediate workaround and one which I recommend to you is to reinstall the apple-gcc42 port without the bootstrap variant; this will probably have a positive overall effect on your ability to install even other ports.
However I will also look into fixing this port for the bootstrap case.