I just noticed while looking into the -fno-common thing that Gem is compiling on Mac OS X using -mmacosx-version-min=10.3 AFAIK, Gem hasn't built on 10.3 in years. From my experience, there are less deployment issues if things are built for the most recent supported version (i.e. 10.4).
.hc
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Computer science is no more related to the computer than astronomy is related to the telescope. -Edsger Dykstra