Infinite wait in fuzzer

[tlively]

Seed 14776223978248778585 at commit 878c96f spins for at least an hour.

[tlively]

Looks like it's because it's using test/./lld/em_asm_pthread.wat as initial contents and that file contains an infinite memory.atomic.wait32. It looks like there are many test files that contain memory.atomic.wait* that are not excluded in scripts/test/fuzzing.py, so I'm not sure why this hasn't come up before.