Fix performance regressions due to lazy initialization.

src/platform-linux.cc

Index: src/platform-linux.cc
diff --git a/src/platform-linux.cc b/src/platform-linux.cc
index 08f4495b53b389cf95de81d74c0f1e582d20ff5d..ca394aafce640fb995981c5070f71640e493b0d0 100644
--- a/src/platform-linux.cc
+++ b/src/platform-linux.cc
@@ -57,6 +57,7 @@
 
 #include "v8.h"
 
+#include "platform-posix.h"
 #include "platform.h"
 #include "v8threads.h"
 #include "vm-state-inl.h"
@@ -105,6 +106,13 @@ void OS::SetUp() {
 }
 
 
+void OS::PostSetUp() {
+  // Math functions depend on CPU features therefore they are initialized after
+  // CPU.
+  MathSetup();
+}
+
+
 uint64_t OS::CpuFeaturesImpliedByPlatform() {
   return 0;  // Linux runs on anything.
 }