Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?

go version devel +beabd87 Tue Mar 8 06:02:15 2016 +0000 freebsd/amd64

1. What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN="/home/rhinofly/home/ds/sandspace/go/bin.freebsd-amd64"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="freebsd"
GOOS="freebsd"
GOPATH="/home/rhinofly/home/ds/sandspace/external/:/home/rhinofly/home/ds/sandspace/golibs/"
GORACE=""
GOROOT="/home/rhinofly/home/ds/sandspace/go"
GOTOOLDIR="/home/rhinofly/home/ds/sandspace/go/pkg/tool/freebsd_amd64"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -gno-record-gcc-switches"
CXX="clang++"
CGO_ENABLED="1"

$ ifconfig -a
em0: flags=8843 metric 0 mtu 1500
    options=209b
    ether 66:30:38:38:64:30
    inet 10.236.12.201 netmask 0xffffff00 broadcast 10.236.12.255 
    nd6 options=29
    media: Ethernet autoselect (1000baseT )
    status: active
lo0: flags=8049 metric 0 mtu 16384
    options=600003
    inet6 ::1 prefixlen 128 
    inet6 fe80::1%lo0 prefixlen 64 scopeid 0x2 
    inet 127.0.0.1 netmask 0xff000000 
    nd6 options=21
    groups: lo 

$ uname -a
FreeBSD rhinofly-devel-800201.localdomain 11.0-CURRENT FreeBSD 11.0-CURRENT #0 r295683: Wed Feb 17 02:07:17 UTC 2016     root@releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

1. What did you do?
   (Use play.golang.org to provide a runnable example, if possible.)

git clone https://github.com/golang/go.git tips-go && cd tips-go/src && ./all.bash

1. What did you expect to see?

build done without error and warning.

1. What did you see instead?

   # runtime/cgo
   runtime/cgo/gcc_amd64.S:47:1: warning: DWARF2 only supports one section per compilation unit
   .section .note.GNU-stack,"",@progbits
   

   (all others build is ok)