Forward port CPU-variant specific toolchains

now controlled by TARGET_KERNEL_TOOLCHAIN_VERSION (so old trees don't use invalid toolchains out of the box
Presently, uses AOSP toolchains by default

to test:     TARGET_KERNEL_TOOLCHAIN_VERSION=linaro-4.9 TARGET_KERNEL_USE_AOSP_TOOLCHAIN=false mka bacon

Change-Id: I3d5e815ed11b640813dda0d6ad2fd7f5bae77c03
build: Parse TARGET_COPY_FILES_OVERRIDES late in the setup

Change-Id: Ie3e4a168ff224e3b65e4627c0757e8813a02167f

Conflicts:

	core/config.mk