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-5.2/src/open.c
===================================================================
--- strace-5.2.orig/src/open.c	2019-07-11 19:51:22.000000000 +0200
+++ strace-5.2/src/open.c	2019-07-22 17:49:41.508766666 +0200
@@ -32,6 +32,10 @@
 #include <linux/openat2.h>
 #include <linux/fcntl.h>
 
+#ifndef O_TMPFILE
+# define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
+#endif
+
 #include "xlat/open_access_modes.h"
 #include "xlat/open_mode_flags.h"
 #include "xlat/open_resolve_flags.h"