test: fix flaky test execute/order-changes-backwards-2-broadcast-and-wait-repeat-message.sb2

Before: sprite 3 uses the `wait` block to wait for the other two sprites
to finish. After the `wait` blocks, sprite 3 sends "end" to the test. If
the sprites take too long to finish, they might not be done before the
"end" message.

After: sprite 3 sets a variable called `finished` to zero on startup,
and increments it every time it hears a new message. Each sprite sends
that new message once it's done. When sprite 3 notices that `finished >=
2`, it sends the "end" message.
This commit is contained in:
Christopher Willis-Ford 2022-07-06 13:18:37 -07:00
parent 8fbf3b465e
commit 281a3e256a