README: points out that you'll need multilib libraries and compiler if you're on amd64.

Signed-off-by: John Floren <john@freyr>

Change-Id: If186ea6e79c4f89e9993aed782c68ab66f077778
Reviewed-on: http://nxm.coreboot.org/review/130
Tested-by: Jenkins QA
Reviewed-by: ron minnich <rminnich@gmail.com>

README

@@ -1,6 +1,7 @@
 How to build:
 
 * Make sure you have Go and Plan 9 Ports installed
+* If you are on a 64-bit system, you will need your distro's appropriate 32-bit libs and compilers installed. That's ia32-libs-dev and libc6-dev-i386 on Debian, which will also pull in the multilib gcc.
 * Copy inferno-os/mkconfig.proto to inferno-os/mkconfig and edit the ROOT, SYSHOST, and OBJTYPE variables
 * Run "sh BUILDTOOLCHAIN"
 * Run ". SETUP"