rewrite and rename issue-53964

Author: Oneirical

src/tools/tidy/src/allowed_run_make_makefiles.txt

@@ -116,7 +116,6 @@ run-make/issue-46239/Makefile
 run-make/issue-47384/Makefile
 run-make/issue-47551/Makefile
 run-make/issue-51671/Makefile
-run-make/issue-53964/Makefile
 run-make/issue-64153/Makefile
 run-make/issue-68794-textrel-on-minimal-lib/Makefile
 run-make/issue-69368/Makefile

tests/run-make/issue-53964/app.rs renamed to tests/run-make/external-crate-panic-handle-no-lint/app.rs

@@ -0,0 +1,16 @@
+// Defining a crate that provides panic handling as an external crate
+// could uselessly trigger the "unused external crate" lint. This test
+// creates this situation and checks that the lint is not triggered.
+// See https://github.com/rust-lang/rust/issues/53964
+
+use run_make_support::{rustc, tmp_dir};
+
+fn main() {
+    rustc().input("panic.rs").run();
+    rustc()
+        .input("app.rs")
+        .panic("abort")
+        .emit("obj")
+        .library_search_path(tmp_dir())
+        .run();
+}