Fix CI (#845)

* Use ubuntu 18.04 instead of 18.10 for MIPS CI

* Fix WASM CI

Author: Amanieu

ci/docker/mipsel-unknown-linux-musl/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:18.10
+FROM ubuntu:18.04
 
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \

crates/stdarch-test/src/wasm.rs

@@ -32,8 +32,8 @@ pub(crate) fn disassemble_myself() -> HashSet<Function> {
     // "wasm-bindgen-test_bg". When running in node this is actually a shim JS
     // file. Ask node where that JS file is, and then we use that with a wasm
     // extension to find the wasm file itself.
-    let js_shim = resolve("wasm-bindgen-test_bg");
-    let js_shim = Path::new(&js_shim).with_extension("wasm");
+    let js_shim = resolve("wasm-bindgen-test");
+    let js_shim = Path::new(&js_shim).with_file_name("wasm-bindgen-test_bg.wasm");
 
     // Execute `wasm2wat` synchronously, waiting for and capturing all of its
     // output. Note that we pass in a custom `maxBuffer` parameter because we're