I can tell by the error message that the version of go you are using when you run go install is not Go 1.5.1. Check your PATH.

I met the same problem. Modify the source code of gomobile/init.go as following:

//if err := installStd(androidArmEnv, "-gcflags=-shared", "-ldflags=-shared"); err != nil {
if err := installStd(androidArmEnv); err != nil {

Recompile gomobile command and try again.

@ianlancetaylor

user@Terminal-T61:~$ go version
go version go1.5.1 linux/386
user@Terminal-T61:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/usr/lib/go/bin:/home/user/Go/bin
user@Terminal-T61:~$ echo $GOROOT
/usr/lib/go

I will revert https://go-review.googlesource.com/#/c/16912/ for now.

go1.5.1 and tip compilers have different flag sets and I cannot easily tell how to make it work for both go1.5 and tip yet.

https://go.googlesource.com/go/+/go1.5.1/src/cmd/go/build.go#341
vs.
https://go.googlesource.com/go/+/master/src/cmd/go/build.go#350

@xuwaters suggestion worked for me, i edited gomobile/init.go, then I put in

sudo apt-get install gcc
sudo GOPATH=/home/user/Go go install -a golang.org/x/mobile/cmd/gomobile

And it worked!
Edit: If anyone could edit the title of the issue to fit it better, Ty!

/cc @crawshaw