detect default TARGET in simd-test-macro

Author: gnzlbg

crates/simd-test-macro/src/lib.rs

@@ -56,7 +56,17 @@ pub fn simd_test(
     let name: TokenStream = name.as_str().parse()
         .expect(&format!("failed to parse name: {}", name.clone().as_str()));
 
-    let target = env::var("TARGET").expect("TARGET environment variable not set");
+    let default_target = if cfg!(target_os = "windows") {
+        Some("x86_64-pc-windows-msvc")
+    } else if cfg!(target_os = "linux") {
+        Some("x86_64-unknown-linux-gnu")
+    } else if cfg!(target_os = "macos") {
+        Some("x86_64-apple-darwin")
+    } else {
+        None
+    };
+
+    let target = env::var("TARGET").unwrap_or_else(|_| default_target.expect("TARGET environment variable not set and no default target known for the current target.").to_string());
     let mut force_test = false;
     let macro_test = match target.split('-').next()
         .expect(&format!("target triple contained no \"-\": {}", target)) {