Add the ability to change the working directory

runtime/bin/directory_win.cc

Index: runtime/bin/directory_win.cc
diff --git a/runtime/bin/directory_win.cc b/runtime/bin/directory_win.cc
index dc6cd699b6855fe2bf26141912ab40f69748ba99..f0f9f9351eeca93a58ce917eca7631504fd47bc2 100644
--- a/runtime/bin/directory_win.cc
+++ b/runtime/bin/directory_win.cc
@@ -425,6 +425,14 @@ char* Directory::Current() {
 }
 
 
+bool Directory::SetCurrent(const char* path) {
+  const wchar_t* system_path = StringUtils::Utf8ToWide(path);
+  bool result = SetCurrentDirectoryW(system_path) != 0;
+  free(const_cast<wchar_t*>(system_path));
+  return result;
+}
+
+
 bool Directory::Create(const char* dir_name) {
   const wchar_t* system_name = StringUtils::Utf8ToWide(dir_name);
   int create_status = CreateDirectoryW(system_name, NULL);