Fix syntax error

src/libunwind/lib.rs

@@ -25,7 +25,7 @@
     }
 }
 
-#[cfg(any(target_env = "musl", target_os = "redox")]
+#[cfg(any(target_env = "musl", target_os = "redox"))]
 #[link(name = "unwind", kind = "static", cfg(target_feature = "crt-static"))]
 #[link(name = "gcc_s", cfg(not(target_feature = "crt-static")))]
 extern {}