Re: HSghc-prim-0.3.1.0.o: unknown symbol 'memcpy'

I rebuilt ghc with clang and gcc; same problem. It works if I add memcpy et al. to libraries/ghc-prim/cbits, but that seems a bad method, as they're available in libc. It seems that I must somehow tell GHC to pull in libc whenever it links against ghc-prim, or to include all needed code from libc in HSghc-prim-0.3.1.0.o. How can I do so? I tried "extra-libraries: c" in ghc-prim.cabal, which fails perplexively, with addDLL: unknown error, tho I disabled building dynamic libraries.