brewkit.rb changes ENV destructively, so lets not do that everytime a formula
is required. Now it's possible for other tools to require a formula
description without worrying about side-effects.
GNU lightning is a library that generates assembly language code
at run-time; it is very fast, making it ideal for Just-In-Time
compilers, and it abstracts over the target CPU, as it exposes to
the clients a standardized RISC instruction set inspired by the
MIPS and SPARC chips.