logger: with MU_LOG_STDOUTERR, write logs to console

For debugging

lib/utils/mu-logger.cc

@@ -122,6 +122,9 @@ Mu::log_init(const std::string& path, Mu::LogOptions opts)
 		return;
 	}
 
+	if (g_getenv("MU_LOG_STDOUTERR"))
+		opts |= LogOptions::StdOutErr;
+
 	MuLogOptions = opts;
 	MuLogPath    = path;
 

lib/utils/mu-logger.hh

@@ -40,6 +40,9 @@ enum struct LogOptions {
  * logging fails -- practically, it goes to the file if there's
  * systemd/journald.
  *
+ * if the environment variable MU_LOG_STDOUTERR is set, LogOptions::StdoutErr is
+ * implied.
+ *
  * @param path path to the log file
  * @param opts logging options
  */