cgpt: Provide a dummy PMBR when no EFI partitions exist

u-boot expects a PMBR to exist when validating a boot media
for EFI interpretation.

BUG=b:33815587
TEST=inspection of resulting flash image

Change-Id: Iad14e298a77368a0ba01453c390f9c25fd651fab
Reviewed-on: https://chromium-review.googlesource.com/423249
Commit-Ready: Ian Coolidge <icoolidge@google.com>
Tested-by: Ian Coolidge <icoolidge@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed