[clang] [C23] Introduce storage-class specifiers for compound literals

Clang has not implemented support for this C23 change.
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3038.htm
https://en.cppreference.com/w/c/language/compound_literal.html
https://godbolt.org/z/P4jG5EfEM
```c
int f() {
    struct f { int f; };
    int i = (constexpr struct f){.f = 42}.f;
    return i;
}
```