build: Use customized entry point for each type of build.

Set an appropriate elf entry point (entry_elf, entry_csm,
reset_vector) for each type of build (coreboot, csm, qemu).  Use that
entry point when determining which sections to keep.

Also, remove the '.export.' mechanism to keep a section in the final
binary - it is no longer used.

This allows the build to slightly reduce the overall size as entry_elf
is no longer needed on non-coreboot builds and entry_csm is no longer
needed on non-csm builds.

Signed-off-by: Kevin O'Connor <>
3 files changed