Fix build without PCH after commit 3ae2387f37

Include errno.h for errno and EEXIST.

Change-Id: Id28d5a08097319eb84b1fe9ef20c9be6ebe575fa
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@theqtcompany.com>

src/corelib/io/qtemporarydir.cpp

@@ -49,6 +49,10 @@
 #include <private/qfilesystemengine_p.h>
 #endif
 
+#if !defined(Q_OS_WIN)
+#include <errno.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 //************* QTemporaryDirPrivate