The current approach of adding SBAT metadata after linking is creating
an image that is badly formed in 2 ways:
* The SBAT section's file offset and size are not a multiple of the
file alignment.
* The SBAT section has a virtual address of zero. EDK2 loads the header
here, and so it gets rejected.
This changes the approach to match shim, where an object file is
created with a .sbat section and then the linker takes care of placing
the section at a more appropriate virtual address.
See https://github.com/vathpela/gnu-efi/pull/14 for the section addition.
