x86/bootblock: Use LDFLAGS_bootblock to enable garbage collection

The x86 bootblock linking is a mess. The bootblock is treated in
a very special manner, and never received the update to link-time
garbage collection.

On newer x86 platforms, the boot media is no longer memory-mapped.
That means we need to do a lot more setup in the bootblock. ROMCC is
unsuitable for this task, and walkcbfs only works on memory-mapped
CBFS. We need to revise the x86 bootflow for this new case.

The approach this patch series takes is to perform CAR setup in the
bootblock, and load the following stage (either romstage or verstage)
from the boot media. This approach is not new, but has been done on
our ARM ports for years.

Since we will be adding .c files to the bootblock, it is prudent to
use link-time garbage collection. This is also consistent to how we
do things on other architectures. Unification FTW!

Change-Id: I16b78456df56e0053984a9aca9367e2542adfdc9
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/11781
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
13 files changed