The gcc45 compilation fails with the following error:
Assume we have the following in /opt/local/etc/macports/macports.conf:
universal_archs x86_64 i386
One needs to edit the portfile of gcc45 as follows:
$ sudo port edit gcc45
Then go to the last line of the configure argument list and add
Don't forget to add the line continuation backslash on the preceding line!
This fixes compilation of gcc45.