fix building coreboot images on i686 hosts

firstly, memtest86+ is currently not cross compiled and
relies on 64-bit headers (x86_64 only). a 32-bit distro
is unlikely to be able to build 64-bit binaries.

secondly: vboot throws a build error due to -Werror when
building on 32-bit hosts. we rely on vboot code to build
cbfstool, so turn off -Werror on vboot

that's all. 32-bit hosts are not recommended; it is assumed
that you are building on an x86_64 host. work will go into
the build system at a later date to make it more portable,
by cross compiling everything, but this should fix 32-bit
for now.

there are some x60/t60 users who still want to build roms,
so let's allow them that possibility.

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/roms

@@ -171,6 +171,8 @@ configure_target()
 	[ -z "$tree" ] && $err "$board: tree not defined"
 
 	[ "${payload_memtest}" != "y" ] && payload_memtest="n"
+	[ "$(uname -m)" = "x86_64" ] || payload_memtest="n"
+
 	[ "${payload_grub_withseabios}" = "y" ] && payload_grub="y"
 	[ "${payload_grub_withseabios}" = "y" ] && \
 		eval "$(setvars "y" payload_seabios payload_seabios_withgrub)"