Add listing for precompiled Windows binaries

They're fixed on wasm-bindgen's CI, so let's download/install them!

src/bindgen.rs

@@ -99,12 +99,15 @@ fn curl(url: &str) -> Result<Vec<u8>, failure::Error> {
 pub fn download_prebuilt_wasm_bindgen(root_path: &Path, version: &str) -> Result<(), Error> {
     let linux = cfg!(target_os = "linux");
     let macos = cfg!(target_os = "macos");
+    let windows = cfg!(windows);
     let x86_64 = cfg!(target_arch = "x86_64");
 
     let target = if linux && x86_64 {
         "x86_64-unknown-linux-musl"
     } else if macos && x86_64 {
         "x86_64-apple-darwin"
+    } else if windows && x86_64 {
+        "x86_64-pc-windows-msvc"
     } else {
         return Err(Error::unsupported(
             "there are no pre-built `wasm-bindgen` binaries for this target",

tests/all/bindgen.rs

@@ -4,16 +4,25 @@ use wasm_pack::bindgen;
 #[test]
 #[cfg(any(
     all(target_os = "linux", target_arch = "x86_64"),
-    all(target_os = "macos", target_arch = "x86_64")
+    all(target_os = "macos", target_arch = "x86_64"),
+    all(windows, target_arch = "x86_64"),
 ))]
 fn can_download_prebuilt_wasm_bindgen() {
+    use std::env;
     let dir = tempfile::TempDir::new().unwrap();
-    bindgen::download_prebuilt_wasm_bindgen(dir.path(), "0.2.19").unwrap();
-    assert!(dir.path().join("bin").join("wasm-bindgen").is_file());
+    bindgen::download_prebuilt_wasm_bindgen(dir.path(), "0.2.21").unwrap();
+    assert!(
+        dir.path()
+            .join("bin")
+            .join("wasm-bindgen")
+            .with_extension(env::consts::EXE_EXTENSION)
+            .is_file()
+    );
     assert!(
         dir.path()
             .join("bin")
             .join("wasm-bindgen-test-runner")
+            .with_extension(env::consts::EXE_EXTENSION)
             .is_file()
     );
 }
@@ -21,11 +30,12 @@ fn can_download_prebuilt_wasm_bindgen() {
 #[test]
 #[cfg(any(
     all(target_os = "linux", target_arch = "x86_64"),
-    all(target_os = "macos", target_arch = "x86_64")
+    all(target_os = "macos", target_arch = "x86_64"),
+    all(windows, target_arch = "x86_64"),
 ))]
 fn downloading_prebuilt_wasm_bindgen_handles_http_errors() {
     let dir = tempfile::TempDir::new().unwrap();
-    let bad_version = "0.2.19-some-trailing-version-stuff-that-does-not-exist";
+    let bad_version = "0.2.21-some-trailing-version-stuff-that-does-not-exist";
     let result = bindgen::download_prebuilt_wasm_bindgen(dir.path(), bad_version);
     assert!(result.is_err());
     let error_msg = result.unwrap_err().to_string();