tango build on mac with dsss and dmd calls ar twice

[Alexy Khrabrov]

So I've tried DSSS out of curiosity on tango on Mac with the new shiny dmd.  BTW build-dmd.sh works, so this is a DSSS trial.

I've got the DSSS.pkg by Anders and changed default to dmd-posix in /usr/etc/rebuild, and culled -version=Posix out of the compile cmd.  

Strangely, it chokes on ar, issuing it twice: first for the ar rc lib objects, then just ar rc lib.  Both invocations are the liblink cmd.  I sense there's something funny going on with the timings here?