GIT_SILENT: include <cerrno> instead of <errno.h>

From /usr/include/c++/10/cerrno:
This is a Standard C++ Library file. You should #include this file
in your programs, rather than any of the *.h implementation files.

agent/priority.cpp

@@ -16,7 +16,7 @@
 #include <QDebug>
 
 #ifndef _WIN32
-#include <errno.h>
+#include <cerrno>
 #include <sys/resource.h>
 #include <sys/syscall.h>
 #include <unistd.h>

debug/akonadisearchdebugdialog.cpp

@@ -4,7 +4,7 @@
   SPDX-License-Identifier: GPL-2.0-or-later
 */
 
-#include <errno.h>
+#include <cerrno>
 
 #include "akonadisearchdebugdialog.h"
 #include "akonadisearchdebugwidget.h"