Introduce runtime/platform directory for code shared between vm

runtime/bin/main.cc

Index: runtime/bin/main.cc
diff --git a/runtime/bin/main.cc b/runtime/bin/main.cc
index 23bf45efa6ee0536a6dfbd31bc1d31247444ed7e..b70226ff372d71acd9ce43816b644ec2b83f005a 100644
--- a/runtime/bin/main.cc
+++ b/runtime/bin/main.cc
@@ -12,9 +12,10 @@
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/file.h"
-#include "bin/globals.h"
 #include "bin/platform.h"
 
+#include "platform/globals.h"
+
 // snapshot_buffer points to a snapshot if we link in a snapshot otherwise
 // it is initialized to NULL.
 extern const uint8_t* snapshot_buffer;