What happened to the "-fod" flag?

[Johannes Pfau]

According to http://gdcproject.org/wiki/UserDocumentation gdc accepts a
"-fod=<directory>" flag to "Specify the object output directory.
Note: this is actually a driver option; the backend ignores it."

That doesn't work for me:
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LANG=C /opt/gdc/bin/gdc -fod=test 
gdc: error: unrecognized command line option '-fod=test'
gdc: fatal error: no input files
compilation terminated.
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Is this flag still supposed to work or is there a replacement?