script: add a script to run CI commands

We want to run some commands to build things for CI, so let's add a
script.  Currently our test commands are very limited, but we may add
additional commands in the future, so let's add a script nevertheless.

Author: bk2204

script/cibuild

@@ -0,0 +1,3 @@
+#!/bin/sh -e
+
+go test ./...