[build.yaml] Try to use wasmerio/setup-wasmer@v2, since `get.wasmer…

….io` is down.

I don't expect this to work, due to https://github.com/wasmerio/setup-wasmer/blob/main/src/index.ts#L45, but at least it's the official GH action.

.github/workflows/build.yaml

@@ -28,11 +28,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
+      - uses: wasmerio/setup-wasmer@v2
       - run: make emsdk
       - run: make build/wasm-test/twsearch-test.wasm
       - run: make build/wasm-single-file/twsearch.mjs
-      - run: curl https://get.wasmer.io -sSfL | sh
-      - run: source ~/.wasmer/wasmer.sh && make test-wasm
       - run: make test-build-js
 
   rust: