build: Include pre-pathmap extra config

 * We need to mess with the pathmap for building simplerecovery in user
   builds, but previously there was no way to do this externally.
 * Source an optional config file before loading the pathmap so that we
   can do some magic without having to set environment variables outside
   the normal build system.

Change-Id: I6132f9e6ffa04678378a5a00ba37b98cd4d9f773
(cherry picked from commit 9c3843330b303cc6c23352b9944e27860a83a23e)
build: Add cafremote command to envsetup

 * So lazy!

Change-Id: I99a988180abb4fb486d4ebbb842bb9eda03bf1bc
(cherry picked from commit ae6df9e0c4ad58f9db60b2bcfbb2c44665f3fd73)