custom: Update README and include example build script

custom/README.md

@@ -1,8 +1,9 @@
 # Custom Logspout Builds
 
 Forking logspout to change modules is unnecessary! Instead, you can create an
-empty Dockerfile based on `gliderlabs/logspout:master` and include a new `modules.go` file for the
-build context that will override the standard one.
+empty Dockerfile based on `gliderlabs/logspout:master` and include a new
+`modules.go` file as well as the `build.sh` script that resides in the root of
+this repo for the build context that will override the standard one.
 
 This directory is an example of doing this. It pairs logspout down to just the
 syslog adapter and TCP transport. Note this means you can only create routes

custom/build.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+set -e
+apk add --update go git mercurial build-base
+mkdir -p /go/src/github.com/gliderlabs
+cp -r /src /go/src/github.com/gliderlabs/logspout
+cd /go/src/github.com/gliderlabs/logspout
+export GOPATH=/go
+go get
+go build -ldflags "-X main.Version $1" -o /bin/logspout
+apk del go git mercurial build-base
+rm -rf /go
+rm -rf /var/cache/apk/*
+
+# backwards compatibility
+ln -fs /tmp/docker.sock /var/run/docker.sock