Auto merge of rust-lang#13478 - Veykril:fix-flycheck, r=Veykril

fix: Fix standard flycheck command not being executed in the workspace it is being invoked for

Fixes rust-lang/rust-analyzer#13477

Author: bors

crates/flycheck/src/lib.rs

@@ -295,7 +295,9 @@ impl FlycheckActor {
             } => {
                 let mut cmd = Command::new(toolchain::cargo());
                 cmd.arg(command);
-                cmd.args(&["--workspace", "--message-format=json"]);
+                cmd.current_dir(&self.root);
+                cmd.args(&["--workspace", "--message-format=json", "--manifest-path"])
+                    .arg(self.root.join("Cargo.toml").as_os_str());
 
                 if let Some(target) = target_triple {
                     cmd.args(&["--target", target.as_str()]);