All patching should be in _preprocess_cmd. config_cmd should just run
configure and nothing else before it, otherwise $PATH is broken when it runs.
Also remove redundant settings to configure, _autoconf already sets them.
We leave explicit AR_FLAGS settings because the builtin rule uses ARFLAGS,
and so would leave AR_FLAGS unset otherwise.
Depends cross compiles project dependencies for linux, mac and windows and multiple architectures.
Depends is original work by Cory Fields and used in bitcoin and a wide range of bitcoin related projects.
