Require SSE2 support for the ia32 port.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index 143bf3ca105c2a32ac7d340a24192d6525ca82d2..1fb6da75ccf636ed63b01f7ced8bea5ff6278d7d 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -55,10 +55,10 @@ static const pthread_t kNoThread = (pthread_t) 0;
 
 uint64_t OS::CpuFeaturesImpliedByPlatform() {
 #if V8_OS_MACOSX
-  // Mac OS X requires all these to install so we can assume they are present.
+  // Mac OS X requires CMOV to install so we can assume it is present.
   // These constants are defined by the CPUid instructions.
   const uint64_t one = 1;
-  return (one << SSE2) | (one << CMOV);
+  return one << CMOV;
 #else
   return 0;  // Nothing special about the other systems.
 #endif