trivial: make clippy work

Conditional compilation around our panic handler has changed in
recently nightly Rust releases.  This updates our cfg directives
to reflect the current state of affairs.

Signed-off-by: Dan Cross <cross@gajendra.net>

Author: Dan Cross

hypatia/src/runtime.rs

@@ -9,7 +9,7 @@
 #[macro_export]
 macro_rules! runtime {
     () => {
-        #[cfg(all(target_os = "none"))]
+        #[cfg(not(test))]
         mod no_std_runtime {
             use core::panic::PanicInfo;