Rollup merge of #148072 - madsmtm:fix-apple-condvar-32bit, r=joboet

Fix compiling `CondVar::wait_timeout` on 32-bit Apple platforms

Fixes rust-lang/rust#147776. I feel like there's a cleaner way to write this, but that probably requires further refactoring.

The build can be tested with `./x build --target arm64_32-apple-watchos` (or with any other 32-bit Apple target).

Tested it works at runtime on an Intel Macbook Pro with macOS 10.12.6, in x86 emulation mode with something similar to `./x test library/std --target x86_64-apple-darwin,i686-apple-darwin`, as well as with a custom test with a timeout of `Duration::from_secs((u32::MAX as u64) + 1)` (which the naive fix would have treated as a duration of 1 second).

r? libs
CC ``@joboet``

Author: jhpratt