Fix linkage on OSX
Fix linkage on OSX

rust-lang-nursery/libc,rust-lang/libc,zethra/libc,superriva/libc,DiamondLovesYou/libc,anatol/libc,diwic/libc,mneumann/libc,philippkeller/libc,zethra/libc,anatol/libc,rust-lang/libc,cactorium/libc,edunham/libc,cybergeek94/libc,cactorium/libc,edunham/libc,mneumann/libc,philippkeller/libc,diwic/libc,DiamondLovesYou/libc,rust-lang-nursery/libc,edunham/libc,philippkeller/libc,cactorium/libc,superriva/libc,DiamondLovesYou/libc,anatol/libc,rust-lang/libc,DiamondLovesYou/libc,diwic/libc,diwic/libc,superriva/libc,cybergeek94/libc,rust-lang-nursery/libc,zethra/libc,cybergeek94/libc,mneumann/libc,edunham/libc