patch 9.0.1557: test failures for unreachable code

Problem:    Test failures for unreachable code.
Solution:   Add a test override to ignore unreachable code.
diff --git a/src/vim9compile.c b/src/vim9compile.c
index b894c6f..03a6e2c 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -3493,7 +3493,8 @@
 		&& ea.cmdidx != CMD_endwhile
 		&& ea.cmdidx != CMD_catch
 		&& ea.cmdidx != CMD_finally
-		&& ea.cmdidx != CMD_endtry)
+		&& ea.cmdidx != CMD_endtry
+		&& !ignore_unreachable_code_for_testing)
 	{
 	    emsg(_(e_unreachable_code_after_return));
 	    goto erret;