build: remove Makefile.build

Remove Makefile.build, as it is not really used by anyone.

Refs: https://github.com/nodejs/node/issues/4607
PR-URL: https://github.com/nodejs/node/pull/5080


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Rich Trott <rtrott@gmail.com>