mapsd: set nice value (#28994)

Co-authored-by: Comma Device <device@comma.ai>

selfdrive/navd/main.cc

@@ -1,6 +1,8 @@
+#include <csignal>
+#include <sys/resource.h>
+
 #include <QApplication>
 #include <QDebug>
-#include <csignal>
 
 #include "selfdrive/ui/qt/util.h"
 #include "selfdrive/ui/qt/maps/map_helpers.h"
@@ -9,6 +11,7 @@
 
 int main(int argc, char *argv[]) {
   qInstallMessageHandler(swagLogMessageHandler);
+  setpriority(PRIO_PROCESS, 0, -20);
 
   QApplication app(argc, argv);
   std::signal(SIGINT, sigTermHandler);