Only require SSE2 at minimum hardware requirement.

runtime/vm/assembler_ia32.h

Index: runtime/vm/assembler_ia32.h
===================================================================
--- runtime/vm/assembler_ia32.h	(revision 15244)
+++ runtime/vm/assembler_ia32.h	(working copy)
@@ -258,14 +258,14 @@
 class CPUFeatures : public AllStatic {
  public:
   static void InitOnce();
-  static bool sse3_supported();
+  static bool sse2_supported();
   static bool sse4_1_supported();
 
  private:
-  static const uint64_t kSSE3BitMask = static_cast<uint64_t>(1) << 32;
+  static const uint64_t kSSE2BitMask = static_cast<uint64_t>(1) << 26;
   static const uint64_t kSSE4_1BitMask = static_cast<uint64_t>(1) << 51;
 
-  static bool sse3_supported_;
+  static bool sse2_supported_;
   static bool sse4_1_supported_;
 #ifdef DEBUG
   static bool initialized_;