Add regression test for rust-lang#107918

Author: GuillaumeGomez

tests/rustdoc-ui/auxiliary/panic-handler.rs

@@ -0,0 +1,9 @@
+// compile-flags: -C panic=abort
+
+#![no_std]
+#![no_main]
+
+#[panic_handler]
+fn panic(_: &core::panic::PanicInfo) -> ! {
+    loop {}
+}

tests/rustdoc-ui/issue-107918.rs

@@ -0,0 +1,11 @@
+// aux-build:panic-handler.rs
+// compile-flags: --document-private-items
+// build-pass
+
+#![no_std]
+#![no_main]
+
+#[panic_handler]
+fn panic(_: &core::panic::PanicInfo) -> ! {
+    loop {}
+}