Make TimingGuard a little safer

Author: bjorn3

src/driver/mod.rs

@@ -73,12 +73,14 @@ impl Drop for TimingGuard {
 
 impl cranelift_codegen::timing::Profiler for MeasuremeProfiler {
     fn start_pass(&self, pass: cranelift_codegen::timing::Pass) -> Box<dyn std::any::Any> {
-        let mut timing_guard =
-            TimingGuard { profiler: std::mem::ManuallyDrop::new(self.0.clone()), inner: None };
+        let mut timing_guard = Box::new(TimingGuard {
+            profiler: std::mem::ManuallyDrop::new(self.0.clone()),
+            inner: None,
+        });
         timing_guard.inner = Some(
             unsafe { &*(&*timing_guard.profiler as &SelfProfilerRef as *const SelfProfilerRef) }
                 .generic_activity(pass.description()),
         );
-        Box::new(timing_guard)
+        timing_guard
     }
 }