Try to switch WASI CI to nightly

RReverser · RReverser · commit d1ae805545c8 · 2019-05-16T13:48:30.000+01:00
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
@@ -38,6 +38,8 @@ jobs:
 - job: wasi
   steps:
     - template: ci/azure-install-rust.yml
+      parameters:
+        toolchain: nightly
     - script: rustup target add wasm32-unknown-wasi
     - script: cargo build --target wasm32-unknown-wasi
 - job: rust_backend
