Or gcc (-fPIC) will complain:
cmd/dist/unix.c: In function ‘cansse2’
cmd/dist/unix.c:774: error: can't find a register in class ‘BREG’ while reloading ‘asm’
cmd/dist/unix.c:774: error: ‘asm’ operand has impossible constraints

This affects bootstrapping on native Darwin/386 where all code is
compiled with -fPIC.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7394047