https://bugs.gentoo.org/show_bug.cgi?id=425252
Index: qwriter-0.1.9-src/qtsingleapplication-2.6-opensource/linux/src/qtlocalpeer.cpp
===================================================================
--- qwriter-0.1.9-src.orig/qtsingleapplication-2.6-opensource/linux/src/qtlocalpeer.cpp
+++ qwriter-0.1.9-src/qtsingleapplication-2.6-opensource/linux/src/qtlocalpeer.cpp
@@ -56,6 +56,7 @@ typedef BOOL(WINAPI*PProcessIdToSessionI
 static PProcessIdToSessionId pProcessIdToSessionId = 0;
 #endif
 #if defined(Q_OS_UNIX)
+#include <unistd.h>
 #include <time.h>
 #endif