assert that --release flag isn't set manually

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Author: onur-ozkan

src/bootstrap/src/core/builder/cargo.rs

@@ -159,6 +159,7 @@ impl Cargo {
     }
 
     pub fn arg(&mut self, arg: impl AsRef<OsStr>) -> &mut Cargo {
+        assert_ne!(arg.as_ref(), "--release");
         self.command.arg(arg.as_ref());
         self
     }