[Bug c/105208] incorrect -Wunused-but-set-variable for static const variables used in const expressions

[muecker at gwdg dot de via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105208

--- Comment #1 from Martin Uecker <muecker at gwdg dot de> ---
Still affects 12.x but seems to have disappeared on trunk.