boot/syslinux: needs an ia32-capable compiler

The pxelinux and isolionux images are 32-bit binaries, so we need a
compiler that can generate them (ie. a compiler that understands -m32).

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Frank Hunleth <fhunleth@troodon-software.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Tested-by: Frank Hunleth <fhunleth@troodon-software.com>
Tested-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>