build system: add easier targetting of cbfstool options per region

The first attempt of providing a options-for-region function to call
to determining a file's cbfstool options would work, but it means there
can only be one instance which has to handle all of the files that may
need an override. That logic can be problematic in impelementation.

Instead, provide a mechanism to target cbfstool options for a given
CBFS region where the implementation is tightly coupled in the build
system to where the file as requested to be added to cbfs. This allows
there to be a base set of cbfstool options while more easily extending
arguments on specific regions.

Example which adds '-b 0x10000' only for the COREBOOT CBFS region:
cbfs-files-y += file.bin
file.bin-COREBOOT-cbfstool-opts := -b 0x10000

Change-Id: Idfafb0205be42768adb04bb0a30fe46a9ca1bd57
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/14640
Tested-by: build bot (Jenkins)
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
1 file changed