Add a free() method for non-cortex-m build targets that panics, to al…

…low checking code that uses it on native platform.

src/interrupt.rs

@@ -77,3 +77,14 @@ where
 
     r
 }
+
+// Make a `free()` function available to allow checking dependencies without specifying a target,
+// but that will panic at runtime if executed.
+#[doc(hidden)]
+#[cfg(not(cortex_m))]
+pub fn free<F, R>(_: F) -> R
+where
+    F: FnOnce(&CriticalSection) -> R,
+{
+    panic!("cortex_m::interrupt::free() is only functional on cortex-m platforms");
+}

src/peripheral/tpiu.rs

@@ -118,7 +118,6 @@ impl TPIU {
     /// [`trace_output_protocol`](Self::set_trace_output_protocol).
     #[inline]
     pub fn trace_output_protocol(&self) -> Option<TraceProtocol> {
-        use core::convert::TryInto;
         self.sppr.read().txmode().try_into().ok()
     }