Fix build, TARGET_CPU_VARIANT must be set

Change-Id: I78f372e22a16d681aeb7ddea2cfb7682fc194ab2
Do custom boot.img without BOARD_CUSTOM_BOOTIMG_MK

This is useful until the custom boot img patch is merged
upstream.

Change-Id: Ib1a20cbb4a48d04d90394ae338c9ba3829e000db
Fix README

The local manifest example was wrong since lt26 has
been removed from AOSP.

Change-Id: Id128aa47e9f9cb3645d0aff90fdb9eb66bd42a0c
Compatibility patches

Change-Id: I2ed2742fad1bdea8f286db02b8a9ba4534afd738
Dont include invensense

Change-Id: I377d929f4f7d7578ce85dee23d5281f10ba67af0
Make it more clear on when to apply_patches

Try to make it a bit more clear that you have to repo sync
before apply_patches.
mkbootimg: Specify custom mkbootimg

Specify custom mkbootimg to generate the boot image for LT26.

Change-Id: I622a44dd7feb734ba05ac5d198f0011d2e09a5a5
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>