all: Add GPU mining, disabled by default

build/flags.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+set -e
+
+if [ ! -f "build/env.sh" ]; then
+    echo "$0 must be run from the root of the repository."
+    exit 2
+fi
+
+# Since Go 1.5, the separator char for link time assignments
+# is '=' and using ' ' prints a warning. However, Go < 1.5 does
+# not support using '='.
+sep=$(go version | awk '{ if ($3 >= "go1.5" || index($3, "devel")) print "="; else print " "; }' -)
+
+# set gitCommit when running from a Git checkout.
+if [ -f ".git/HEAD" ]; then
+    echo "-ldflags '-X main.gitCommit$sep$(git rev-parse HEAD)'"
+fi
+
+if [ ! -z "$GO_OPENCL" ]; then
+   echo "-tags opencl"
+fi