respect the required rt feature

tokio/src/macros/select.rs

@@ -526,7 +526,7 @@ doc! {macro_rules! select {
 
                 // Return `Pending` when the task budget is depleted since budget-aware futures
                 // are going to yield anyway and other futures will not cooperate.
-                ::std::task::ready!($crate::task::poll_budget_available(cx));
+                ::std::task::ready!($crate::macros::support::poll_budget_available(cx));
 
                 for i in 0..BRANCHES {
                     let branch;

tokio/src/macros/support.rs

@@ -7,6 +7,13 @@ cfg_macros! {
     pub fn thread_rng_n(n: u32) -> u32 {
         crate::runtime::context::thread_rng_n(n)
     }
+
+    pub fn poll_budget_available(cx: &mut std::task::Context<'_>) -> std::task::Poll<()> {
+        #[cfg(feature = "rt")]
+        { crate::task::poll_budget_available(cx) }
+        #[cfg(not(feature = "rt"))]
+        { std::task::Poll::Ready(()) }
+    }
 }
 
 pub use std::future::{Future, IntoFuture};

tokio/tests/macros_select.rs

@@ -630,7 +630,7 @@ async fn mut_ref_patterns() {
     };
 }
 
-#[maybe_tokio_test]
+#[tokio::test]
 async fn select_is_budget_aware() {
     const BUDGET: usize = 128;