Name builder steps

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

gateway/Dockerfile

-FROM golang:1.7.5
+FROM golang:1.7.5 as build
 WORKDIR /go/src/github.com/alexellis/faas/gateway
 
 COPY vendor         vendor
@@ -22,7 +22,7 @@ EXPOSE 8080
 ENV http_proxy      ""
 ENV https_proxy     ""
 
-COPY --from=0 /go/src/github.com/alexellis/faas/gateway/gateway    .
+COPY --from=build /go/src/github.com/alexellis/faas/gateway/gateway    .
 
 COPY assets     assets
 

gateway/build.sh

 #!/bin/sh
 
-export TAG="latest-dev"
-echo Building functions/gateway:$TAG
+export eTAG="latest-dev"
+echo $1
+if [ $1 ] ; then
+  echo "set this"
+  eTAG=$1
+fi
+
+echo Building functions/gateway:$eTAG
 
 docker build --build-arg https_proxy=$https_proxy --build-arg http_proxy=$http_proxy \
-  -t functions/gateway:$TAG .
+  -t functions/gateway:$eTAG .
+