[Bug c++/121524] [15/16 Regression] Trailing alignas leaks into subsequent types, sometimes

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121524

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
-pedantic-errors also rejects this:
```
<source>:8:29: error: 'alignas' on a type other than class [-Wattributes]
    8 |         UT foo[8] alignas(32);
      |                             ^
```