test io_timeout_timedout fails on aarch64 and mips64el

[jonassmedegaard]

I have packaged async-std for Debian, where it succesfully builds on all supported architctures except aarch64 and mips64el where it fails test io_timeout_timedout:

     Running `/<<PKGBUILDDIR>>/target/aarch64-unknown-linux-gnu/release/deps/io_timeout-aa97540a6076f5ab`

running 3 tests
test io_timeout_future_ok ... ok
test io_timeout_timedout - should panic ... FAILED
test io_timeout_future_err - should panic ... ok

failures:

---- io_timeout_timedout stdout ----
note: test did not panic as expected

failures:
    io_timeout_timedout

test result: FAILED. 2 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.08s

Commit e4c4c93d2 talks about 32bit archs in its commit message, however skips that very test not only for 32bit archs, and I wonder if perhaps the logic should be reversed to only enable that test on known working architectures?