Add armhf build steps

This will help with CI for ARMHF

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

gateway/push.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+set -e
+
+export arch=$(uname -m)
+
+export eTAG="latest-dev"
+
+if [ "$arch" = "armv7l" ] ; then
+   eTAG="latest-armhf-dev"
+fi
+
+echo "$1"
+if [ "$1" ] ; then
+  eTAG=$1
+  if [ "$arch" = "armv7l" ] ; then
+    eTAG="$1-armhf"
+  fi
+fi
+
+echo Pushing openfaas/gateway:$eTAG
+
+docker push openfaas/gateway:$eTAG
+