Merge #1442

1442: testsuite: test for diagnostics shown when a built-in macro does not exist r=CohenArthur a=liushuyu

- testsuite: test for diagnostics shown when a built-in macro does not exist

Co-authored-by: liushuyu <liushuyu011@gmail.com>

gcc/testsuite/rust/compile/builtin_macro_not_found.rs

@@ -0,0 +1,4 @@
+#[rustc_builtin_macro]
+macro_rules! crabby_crab_carb { // { dg-error "cannot find a built-in macro with name .crabby_crab_carb." }
+    () => {{}};
+}