Update to wasm32-wasip1-based testing

This commit is a replacement for rust-lang#1417 now that rust-lang/rust#12046 has
landed. While I was here I went ahead and updated the Wasmtime used in
CI and adapted its command line as well.

.github/workflows/main.yml

@@ -81,7 +81,7 @@ jobs:
         #- mips64el-unknown-linux-gnuabi64
         #- mipsel-unknown-linux-musl
         - s390x-unknown-linux-gnu
-        - wasm32-wasi
+        - wasm32-wasip1
         - i586-unknown-linux-gnu
         - nvptx64-nvidia-cuda
         - thumbv6m-none-eabi
@@ -135,7 +135,7 @@ jobs:
           disable_assert_instr: true
         - target: s390x-unknown-linux-gnu
           os: ubuntu-latest
-        - target: wasm32-wasi
+        - target: wasm32-wasip1
           os: ubuntu-latest
         - target: aarch64-apple-darwin
           os: macos-latest

ci/docker/wasm32-wasip1/Dockerfile

@@ -0,0 +1,13 @@
+FROM ubuntu:20.04
+
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update -y && apt-get install -y --no-install-recommends \
+  ca-certificates \
+  curl \
+  xz-utils \
+  clang
+
+RUN curl -L https://github.com/bytecodealliance/wasmtime/releases/download/v18.0.2/wasmtime-v18.0.2-x86_64-linux.tar.xz | tar xJf -
+ENV PATH=$PATH:/wasmtime-v18.0.2-x86_64-linux
+
+ENV CARGO_TARGET_WASM32_WASIP1_RUNNER="wasmtime --dir /checkout/target/wasm32-wasip1/release/deps::."