Add -mno-movbe to disable "movbe" instruction from code-gen

Intruction "movbe" (move data after swapping bytes) is only available in
Intel atom.  Disable it for more general x86 devices and x86 hosts which
run emulator-x86.  Although emulator-x86 can support "movbe", most of
the time we want to run emulator-x86 with VT support for speed (with KVM
in Linux, or HAXM in Windows/MacOSX).  The presence of "movbe" can crash
emulator-x86 in VT because non-atom host doesn't have it natively.

Change-Id: I86e037900ddcb8d544f92b8d8464c8627347e560
diff --git a/core/combo/ b/core/combo/
index a4d07b5..cb251d3 100644
--- a/core/combo/
+++ b/core/combo/
@@ -132,6 +132,11 @@
+# instructions "movbe" is only available in Intel atom.  Disable it
+# for general x86 device and x86 host which runs emulator-x86
 # XXX: This flag is probably redundant since our toolchain binaries already
 # generate 32-bit machine code. It probably dates back to the old days
 # where we were using the host toolchain on Linux to build the platform