libmain: add progress bar with multiple status lines

Add the log-formats `multiline` and `multiline-with-logs` which offer
multiple current active building status lines.

Change-Id: Idd8afe62f8591b5d8b70e258c5cefa09be4cab03

src/libmain/loggers.hh

@@ -11,6 +11,8 @@ enum class LogFormat {
   internalJSON,
   bar,
   barWithLogs,
+  multiline,
+  multilineWithLogs,
 };
 
 void setLogFormat(const std::string & logFormatStr);