[Bug c++/90736] [9/10 Regression] Bogus error with alignas

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90736

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
This compiles when the parm 'b' is not const.