Relay server for custom builds of syncthing android

I tried following the above mentioned steps on a linux box. I have hit a roadblock with the following error when I run the following command

command: CGO_ENABLED=1 CC=/usr/local/android-24-arm/bin/arm-linux-androideabi-gcc \ go run build.go -goos android -goarch arm build

error cmd/syncthing/gui_statics.go:37: undefined: auto.Assets cmd/syncthing/gui_statics.go:44: undefined: auto.Assets exit status 2 exit status 1

I have read the following related post, but the steps mentioned are not working for me: