hammerhead: remove custom toolchain for now

kernel has randomly start up problems with linaro 4.8. Use default toolchain
till problem is identified

Change-Id: Ib4d9c1d9151297f86782b82cc7e462b6ea2a29a0
Revert "hammerhead: readd DSP library"

This reverts commit 56bedddf958d2c74dc26034d5f9eb299693e5484.

Change-Id: If5cd355ed5ae33e855969b0ee50c622cecb80165
hammerhead: force builder to have vendor repos to compile

We have a lot unofficial builders who forget to fetch the binaries needed
for the device. The build will error out now if it was forgotten.

Change-Id: I8fba0122ce28022446f357ff17112a6e3ef61f0c
Merge remote-tracking branch 'slim/lp5.0' into lp

Conflicts:
	BoardConfig.mk