arm: make libcgo build during OS X cross-compile
arm: make libcgo build during OS X cross-compile

The gcc on OS X seems pickier about noticing
symbols that are referred to but not found during
the link of a .so file.

R=r
CC=golang-dev
http://codereview.appspot.com/2098047

scirelli/scirelli-go,npe9/noahevans-go9,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,npe9/noahevans-go9,rflanagan/reginaldflanagan-project1,Triskite/willstone-goclone,scirelli/scirelli-go,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,mhennings/marcohennings-go,Triskite/willstone-goclone,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,bryanxu/go-zh,Triskite/willstone-goclone,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,glycerine/jeaten-go-arrayof-structof,d0f/go-zh,rdp/rogerpack2005-golang,sanjosh/sanjos100-tipc,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,webfd/go-zh,bryanxu/go-zh,Triskite/willstone-goclone,d0f/go-zh,scirelli/scirelli-go,mhennings/marcohennings-go,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,scirelli/scirelli-go,sanjosh/sanjos100-tipc,webfd/go-zh,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,rflanagan/reginaldflanagan-project1,npe9/noahevans-go9,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,mhennings/marcohennings-go,Triskite/willstone-goclone,npe9/noahevans-go9,webfd/go-zh,d0f/go-zh,mhennings/marcohennings-go,d0f/go-zh,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,npe9/noahevans-go9,webfd/go-zh,d0f/go-zh,Triskite/willstone-goclone,d0f/go-zh,sanjosh/sanjos100-tipc,Triskite/willstone-goclone,webfd/go-zh,Triskite/willstone-goclone,rdp/rogerpack2005-golang,npe9/noahevans-go9,scirelli/scirelli-go,npe9/noahevans-go9,mhennings/marcohennings-go,webfd/go-zh,scirelli/scirelli-go,bryanxu/go-zh,bryanxu/go-zh,scirelli/scirelli-go