Don't duplicate OS::CpuFeaturesImpliedByPlatform for every POSIX platform.

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index 8ec4c510403899ee7ac39ad4cf3e7435f59ba074..10aef80d9caa7317323e4b379acdc5fe68f7ca93 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -231,14 +231,6 @@ void OS::SignalCodeMovingGC() {
 }
 
 
-uint64_t OS::CpuFeaturesImpliedByPlatform() {
-  // MacOSX requires all these to install so we can assume they are present.
-  // These constants are defined by the CPUid instructions.
-  const uint64_t one = 1;
-  return (one << SSE2) | (one << CMOV) | (one << RDTSC) | (one << CPUID);
-}
-
-
 int OS::ActivationFrameAlignment() {
   // OS X activation frames must be 16 byte-aligned; see "Mac OS X ABI
   // Function Call Guide".