Another testcase update needed for my r12-1405 commit.
gcc/testsuite/ChangeLog:
* gcc.dg/c2x-attr-maybe_unused-1.c: Expect no warnings.
struct [[maybe_unused]] s { double d; };
-struct s2 { [[__maybe_unused__]] int a; int b [[maybe_unused]]; } x; /* { dg-warning "attribute ignored" } */
+struct s2 { [[__maybe_unused__]] int a; int b [[maybe_unused]]; } x;
enum e { E1 [[maybe_unused]] };
enum [[maybe_unused]] eu { E2 };
-union u2 { [[maybe_unused]] int a; int b [[maybe_unused]]; } y; /* { dg-warning "attribute ignored" } */
+union u2 { [[maybe_unused]] int a; int b [[maybe_unused]]; } y;