[PATCH] Update bindings for the wasm32-wasi target

[PATCH] Update bindings for the wasm32-wasi target

This commit performs a number of updates for libc with the `wasm32-wasi`
target:

* Updates the `wasi-libc` repository commit used (previously known as
  `wasi-sysroot`)
* Updates the container to Ubuntu 19.10 which has Clang 9 packaged which
  is all we need.
* Avoids building `wasmtime` and instead downloads a precompiled binary.
* Updates bindings in `src/wasi.rs` to match the current upstream state.

Gbp-Pq: Name u-wasm32-libc-1625.patch