Split out libplatform into a separate libary

src/mksnapshot.cc

Index: src/mksnapshot.cc
diff --git a/src/mksnapshot.cc b/src/mksnapshot.cc
index 69306e14dc5ee79b9d72b7e7b7a0a6e154d7293f..03c693568eac85357099ad1927cd1feb3c5eace2 100644
--- a/src/mksnapshot.cc
+++ b/src/mksnapshot.cc
@@ -11,6 +11,7 @@
 
 #include "src/v8.h"
 
+#include "include/libplatform/libplatform.h"
 #include "src/assembler.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
@@ -317,6 +318,9 @@ void DumpException(Handle<Message> message) {
 
 int main(int argc, char** argv) {
   V8::InitializeICU();
+  v8::Platform* platform =
+      v8::platform::CreateDefaultPlatform(base::OS::NumberOfProcessorsOnline());
+  v8::V8::InitializePlatform(platform);
   i::Isolate::SetCrashIfDefaultIsolateInitialized();
   i::CpuFeatures::Probe(true);
 
@@ -441,5 +445,7 @@ int main(int argc, char** argv) {
 
   isolate->Dispose();
   V8::Dispose();
+  V8::ShutdownPlatform();
+  delete platform;
   return 0;
 }