Some buildroots provide version of kernel-headers package that do not yet
contains O_TMPFILE definition.  Since (looks like) there were none discrepancies
in O_TMPFILE definition in RHEL, work that around by providing a fallback
definition of O_TMPFILE.
Index: strace-4.24/open.c
===================================================================
--- strace-4.24.orig/open.c	2018-08-09 01:27:06.000000000 +0200
+++ strace-4.24/open.c	2018-08-23 13:17:20.666260200 +0200
@@ -48,6 +48,10 @@
 # endif
 #endif
 
+#ifndef O_TMPFILE
+# define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
+#endif
+
 #include "xlat/open_access_modes.h"
 #include "xlat/open_mode_flags.h"