Update the bundled wasi-libc with libstd

This just updates WASI libc, in preparation for WASI reactor support in
a separate change.

Author: sunfishcode

src/ci/docker/host-x86_64/dist-various-2/build-wasi-toolchain.sh

@@ -9,10 +9,10 @@ curl https://ci-mirrors.rust-lang.org/rustc/clang%2Bllvm-9.0.0-x86_64-linux-gnu-
   tar xJf -
 export PATH=`pwd`/clang+llvm-9.0.0-x86_64-linux-gnu-ubuntu-14.04/bin:$PATH
 
-git clone https://github.com/CraneStation/wasi-libc
+git clone https://github.com/WebAssembly/wasi-libc
 
 cd wasi-libc
-git reset --hard 9efc2f428358564fe64c374d762d0bfce1d92507
+git reset --hard 215adc8ac9f91eb055311acc72683fd2eb1ae15a
 make -j$(nproc) INSTALL_DIR=/wasm32-wasi install
 
 cd ..