efi_loader: support building UEFI binaries on sandbox

On the sandbox the UEFI binaries must match the host architectures.

Adjust the Makefiles. Provide the PE/COFF header and relocation files.

Allow building helloworld.efi on the sandbox.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
7 files changed