xtask: feature specific target dirs

xtask/src/main.rs

@@ -329,9 +329,15 @@ fn cargo_exec(
         None
     };
 
+    let target_dir = METADATA
+        .get()
+        .unwrap()
+        .target_directory
+        .join(format!("xtargets/{renderer}"));
+    std::fs::create_dir_all(&target_dir)?;
+
     let output = duct::cmd("cargo", args)
-        .stdout_capture()
-        .stderr_capture()
+        .env("CARGO_TARGET_DIR", target_dir)
         .reader()?;
 
     Ok(