Integrate head.S directly into libc and remove all instances of head.o. * Drop 'separate class' entry for head.S. * Drop special treament for head.o inside lpgcc. * Change the .text in `x86/head.S` to `.section .text._entry`. * Drop arch/mock/head.c, initially added as a dummy file. Change-Id: I156d781908fcc38d455bbf9f2c29e5ab95c7775a Signed-off-by: Subrata Banik <subratabanik@google.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/82478 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Julius Werner <jwerner@chromium.org>