Modified examples Makefile to only build the ExceptionDemo example for

x86 and x86_64 on UNIX systems. Only OS X 10.6.2 (x86_64) and 32bit CentOS 5.2
with gcc 4.1.2 were tested. ARM UNIX build triggered failure motivating this
modification, as it seems that the ARM ABI does not support _Unwind_GetIP(...),
_Unwind_SetGR(...), and _Unwind_SetIP(...). From doing a quick browse of:
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf,
it seems as if all other exception related apis are supported. Looks like
the port can be done to ARM. Thanks to Xerxes Rånby <xerxes@zafena.se> for
pointing out this error.

llvm-svn: 96949