Fix breakage from rust-lang#56988 and workaround for rust-lang#57569

Author: Vardhan Thigle

src/libstd/sys/sgx/time.rs

@@ -25,6 +25,14 @@ impl Instant {
     pub fn checked_sub_duration(&self, other: &Duration) -> Option<Instant> {
         Some(Instant(self.0.checked_sub(*other)?))
     }
+
+    pub fn actually_monotonic() -> bool {
+        false
+    }
+
+    pub const fn zero() -> Instant {
+        Instant(Duration::from_secs(0))
+    }
 }
 
 impl SystemTime {

src/libstd/sys/sgx/waitqueue.rs

@@ -456,6 +456,7 @@ mod spin_mutex {
         }
     }
 
+    /// Lock the Mutex or return false.
     pub macro try_lock_or_false {
         ($e:expr) => {
             if let Some(v) = $e.try_lock() {