LibNativeBridge: Add early init & env setup

Add a method to set up /proc/cpuinfo with enough privileges. Set
up the environment for an app in InitializeNativeBridge().

Turn on -Wall for libnativebridge.

(cherry picked from commit 962eb40a)
(cherry picked from commit ab0da5a9)
(cherry picked from commit 2f71cb24)
(cherry picked from commit 04054e28)
(cherry picked from commit 4390a632)

Bug: 17671501
Change-Id: Id4f4127d82737b5e56a77175e1068ff5cea60f9d