Change Directory.create to not fail on existing directory with that name.

runtime/bin/directory_macos.cc

Index: runtime/bin/directory_macos.cc
diff --git a/runtime/bin/directory_macos.cc b/runtime/bin/directory_macos.cc
index 7adb80f9156ab2d308131aee2181243b35b85a27..59977a3886dd54334f2e220fb5cc12a5d487afb8 100644
--- a/runtime/bin/directory_macos.cc
+++ b/runtime/bin/directory_macos.cc
@@ -381,6 +381,9 @@ char* Directory::Current() {
 
 
 bool Directory::Create(const char* dir_name) {
+  // If the directory already exists and is a directory do not
+  // attempt to create it again and treat it as a success.
+  if (Exists(dir_name) == EXISTS) return true;
   // Create the directory with the permissions specified by the
   // process umask.
   return (TEMP_FAILURE_RETRY(mkdir(dir_name, 0777)) == 0);