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

dsriram/golang,ssrl/go,tv42/old-go,tv42/old-go,apparentlymart/golang,gnanderson/go,gnanderson/go,tv42/old-go,gnanderson/go,ssrl/go,pombredanne/go-deleteme,gnanderson/go,ssrl/go,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,h8liu/golang,dsriram/golang,apparentlymart/golang,h8liu/golang,pombredanne/go-deleteme,ssrl/go,gnanderson/go,apparentlymart/golang,tv42/old-go,dsriram/golang,pombredanne/go-deleteme,dsriram/golang,dsriram/golang,apparentlymart/golang,pombredanne/go-deleteme,ssrl/go,h8liu/golang,h8liu/golang,gnanderson/go,apparentlymart/golang,h8liu/golang,ssrl/go,dsriram/golang,h8liu/golang,tv42/old-go,apparentlymart/golang,pombredanne/go-deleteme,ssrl/go,pombredanne/go-deleteme,apparentlymart/golang,h8liu/golang,gnanderson/go