pcr: libreboot-utils: fix cbfstool compilation on 32bit architectures
    
    On i686, cbfstool wasn't build because it failed to compile, and on
    armv7h, the build fail with an error similar to this one:
        host/lib/extract_vmlinuz.c: In function ‘ExtractVmlinuz’:
        host/lib/extract_vmlinuz.c:67:9: warning:
        ‘memcpy’ specified bound between 2147483648 and 4294967295
        exceeds maximum object size 2147483647 [-Wstringop-overflow=]
           67 |         memcpy(vmlinuz, kpart_data + vmlinuz_header_offset,
              |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           68 |                vmlinuz_header_size);
              |                ~~~~~~~~~~~~~~~~~~~~
    
    This fixes that build error and enables cbfstool to be built on all the
    architectures supported by Parabola.
    
    Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>