Revert "Revert "Ensure necessary external storage dirs while creating sandboxes.""

This reverts commit 88114b2a563d5bbbc68a16566e223797f4136227.

Reason for revert: blocking issue in b/124345887 is resolved

Change-Id: Ie34843c12b7a471d2384b64ad049ede63aed09e8
diff --git a/Utils.h b/Utils.h
index 574bcd4..9a1fa09 100644
--- a/Utils.h
+++ b/Utils.h
@@ -63,6 +63,9 @@
 /** Calls unlink(2) at linkpath */
 status_t Unlink(const std::string& linkpath);
 
+/** Creates the given directory if it is not already available */
+status_t CreateDir(const std::string& dir, mode_t mode);
+
 bool FindValue(const std::string& raw, const std::string& key, std::string* value);
 
 /* Reads filesystem metadata from device at path */