Auto merge of #1968 - de-vri-es:accept4-old-android, r=JohnTitor

Implement accept4 on Android as raw syscall.

This PR implements `accept4()` on Android using `syscall()` instead of the `accept4()` wrapper.

This is done because the `accept4()` wrapper wasn't added to Androids `libc` until version 5.0 (API level 21). By using `syscall` directly, `accept4` will also work on older  Android versions.

The kernel itself has supported it since Linux 2.6.28, which was shipped with stock Android since version 1.6 already: https://en.wikipedia.org/wiki/Android_version_history#Android_1.6_Donut_(API_4)

At the moment, the CI for the rust repo still uses API level 14. Although I also opened a PR to bump that too: https://github.com/rust-lang/rust/pull/78601. However, it might make sense to keep the old API level in CI if this is merged.