AU: Mix stdout and stderr together in the logs.

subprocess.h

Index: subprocess.h
diff --git a/subprocess.h b/subprocess.h
index 6685f4d669f7eccbd1bc22608227e69ecd1c7cfe..8f97c5d2b8be5a8938b946908e7d66fe2c80edac 100644
--- a/subprocess.h
+++ b/subprocess.h
@@ -63,6 +63,10 @@ class Subprocess {
   // requested callback.
   static void GChildExitedCallback(GPid pid, gint status, gpointer data);
 
+  // Callback which runs in the child before exec to redirect stderr onto
+  // stdout.
+  static void GRedirectStderrToStdout(gpointer user_data);
+
   struct SubprocessCallbackRecord {
     ExecCallback callback;
     void* callback_data;