```
(venv) spacetanuki% TOYWASM=~/git/toywasm/b/toywasm python3 test-runner/wasi_test_runner.py -t ~/git/wasm/wasi-threads/test/testsuite -r ~/git/toywasm/test/wasi-testsuite-adapter.py
Test wasi_threads_exit_nonmain_wasi passed
Test wasi_threads_exit_main_busy passed
Test wasi_threads_exit_main_wasi passed
Test wasi_threads_exit_nonmain_busy passed
Test wasi_threads_spawn passed
Test wasi_threads_exit_main_block passed
Test wasi_threads_exit_nonmain_block passed

===== Test results =====
Runtime: toywasm v0.0
Suite: WASI threads proposal
  Total: 7
  Passed:  7
  Failed:  0

Test suites: 1 passed, 0 total
Tests:       7 passed, 0 total
(venv) spacetanuki%
```

as suggested in WebAssembly/wasi-libc#369

the corresponding toywasm change:
yamt/toywasm@4d81846

```
spacetanuki% TOYWASM=~/git/toywasm/b/toywasm python3 ~/git/wasm/wasi-testsuite/test-runner/wasi_test_runner.py -t ./test/testsuite -r ~/git/toywasm/test/wasi-testsuite-adapter.py
Test wasi_threads_exit_nonmain_wasi passed
Test wasi_threads_exit_main_busy passed
Test wasi_threads_exit_main_wasi passed
Test wasi_threads_exit_nonmain_busy passed
Test wasi_threads_spawn passed
Test wasi_threads_exit_main_block passed
Test wasi_threads_exit_nonmain_block passed

===== Test results =====
Runtime: toywasm v0.0
Suite: WASI threads proposal
  Total: 7
  Passed:  7
  Failed:  0

Test suites: 1 passed, 0 total
Tests:       7 passed, 0 total
spacetanuki%
```

While it's a bit redundant to both import and export a memory,
it's what WASI implementations expect.

Emscripten, toywasm:
Import alone is fine. But export wouldn't hurt.

wasm-micro-runtime:
Export is checked. Nothing actually seems to rely on it though.

wasmtime:
Export is necessary?

References:
https://github.com/WebAssembly/WASI/blob/main/legacy/application-abi.md#current-unstable-abi
WebAssembly#22

Also add some comments

While I suspect wait and notify are memory barriers for most
implementations, it's safer to issue explicit fences.

cf.
WebAssembly#26
WebAssembly/wasi-libc#387