cabal: library archive index and Mac OS X?

I've gotten a bug report that Mac OS X complains when trying to link against cabal-generated archives, because it lacks an index:

ghc --make Main -o prog Chasing modules from: Test Compiling Main ( Test.hs, Test.o ) Linking ... ld: archive: /usr/local/lib/uust-1.0/libHSuust-1.0.a has no table of contents, add one with ranlib(1) (can't load from it)

In reading the man page of ranlib (on Linux), it sounds like an optional optimization. It also looks like a "-s" flag to ar will generate the index, so that's easy enough to fix. Can anyone explain to me whether / why Mac OS X needs this index, and whether it'll hurt for any other arches? Should we just pass the -s flag to ar? peace, isaac