[liftoff] Add a code comment to landing pads

This makes it much easier to read the code, since that code otherwise
looks unreachable.

R=thibaudm@chromium.org

Change-Id: I8720f8e23a6932d83b7ef6a1f26632095ecfeb43
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2826120Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74005}

src/wasm/baseline/liftoff-compiler.cc

@@ -4072,6 +4072,7 @@ class LiftoffCompiler {
     __ emit_jump(&skip_handler);
 
     // Handler: merge into the catch state, and jump to the catch body.
+    DEBUG_CODE_COMMENT("-- landing pad --");
     __ bind(handler.get());
     __ ExceptionHandler();
     __ PushException();