Error when building universal binary

[Jacob Carlborg]

I'm trying to build a universal binary on Mac OS X 10.5.4 using the gdc 
bundle from the tango website: 
http://www.dsource.org/projects/tango/wiki/GdcDownloads

I'm using the "-arch" option and I get this error:
cc1d: error: unrecognized command line option "-arch"
(it doesn't matter if I use gdc or gdmd)

Doesn't gdc support the "-arch" option? I thought that if it worked with 
gcc it would also work with gdc.