Update Blueprint link in `README.md` to point to Android's version.

## Build logic

The build logic is written in Go using the

[blueprint](http://godoc.org/github.com/google/blueprint) framework.  Build

logic receives module definitions parsed into Go structures using reflection

and produces build rules.  The build rules are collected by blueprint and

written to a [ninja](http://ninja-build.org) build file.

[blueprint](https://android.googlesource.com/platform/build/blueprint)

framework.  Build logic receives module definitions parsed into Go structures

using reflection and produces build rules.  The build rules are collected by

blueprint and written to a [ninja](http://ninja-build.org) build file.

## Environment Variables Config File