Add the ability to change the working directory

runtime/bin/directory_android.cc

Index: runtime/bin/directory_android.cc
diff --git a/runtime/bin/directory_android.cc b/runtime/bin/directory_android.cc
index 7c30274f15f8b83dd5d8f6a40c711451defbe3bd..24193f9de9997ade7b39e57f78749edd5b838f31 100644
--- a/runtime/bin/directory_android.cc
+++ b/runtime/bin/directory_android.cc
@@ -429,6 +429,12 @@ char* Directory::Current() {
 }
 
 
+bool Directory::SetCurrent(const char* path) {
+  int result = TEMP_FAILURE_RETRY(chdir(path));
+  return result == 0;
+}
+
+
 bool Directory::Create(const char* dir_name) {
   // Create the directory with the permissions specified by the
   // process umask.