Attempt transition to ui test

Author: Oneirical

tests/run-make/external-crate-panic-handle-no-lint/app.rs

@@ -0,0 +1,15 @@
+//@ compile-flags: -Cpanic=abort --emit=obj
+
+// Defining a crate that provides panic handling as an external crate
+// could uselessly trigger the "unused external crate" lint. This was fixed,
+// and this test checks that the fix did not break compiler functionality.
+// See https://github.com/rust-lang/rust/issues/53964
+
+#![crate_type = "bin"]
+#![no_main]
+#![no_std]
+
+#![deny(unused_extern_crates)]
+
+// `panic` provides a `panic_handler` so it shouldn't trip the `unused_extern_crates` lint
+extern crate panic;