add support for overriding build.prop settings.

Change-Id: Ie4224d608b7bcb0c2087bd77bc954f8f5f9b6495

Conflicts:
	core/product_config.mk
kernel.mk: Use standard toolchain paths

Change-Id: I1225fd05dcedcff03a1cf1102841cbd010b609cf

Conflicts:
	core/tasks/kernel.mk
build: recovery: don't remove init.*.rc

Change-Id: Ic1e14e1e82cb28106da5b39f530e0b667377840d
Fix building custom recovery with userdebug

Credit Koushik Dutta

Change-Id: I41f1a91849f3aab435a3398696149afce68d8708