MacPorts recorded graphviz-oldgui was installed with arch i386 but it actually installed arch ppc

[Ryan Schmidt]

graphviz-oldgui installs a pre-compiled binary; source is not available. The binary is ppc-only so in r68725 I added "supported_archs ppc". I was surprised then to see that on my Snow Leopard Mac MacPorts recorded in the registry that this port was installed with the arch i386:

$ port -v installed graphviz-oldgui
The following ports are currently installed:
  graphviz-oldgui @16_0 (active) platform='darwin 10' archs='i386'

I had expected to see "archs='ppc'" not "archs='i386'".

I filed this as #25219 but Joshua closed it as invalid, saying I should write "configure.build_arch ppc".

I don't understand why the value MacPorts automatically set configure.build_arch to was not one of the archs supported by the port nor why this is not considered a bug.