build: add strace output to test_race.sh script

contrib/test_race.sh

@@ -9,5 +9,9 @@ fi
 
 for i in {1..60}; do
     echo "running $i ..."
-    flow --exec quit "$@" || exit 1
+    # flow --exec quit "$@" || exit 1
+    strace -f -t \
+        -e trace=open,openat,close,socket,pipe,pipe2,dup,dup2,dup3,fcntl,accept,accept4,epoll_create,epoll_create1,eventfd,timerfd_create,signalfd,execve,fork \
+        -o trace.log \
+        flow --exec quit --trace-level 9 "$@"
 done