[Bug middle-end/90302] Implement __builtin_warning

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90302

--- Comment #4 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
There is a prototype patch by Martin Sebor at

https://gcc.gnu.org/pipermail/gcc-patches/2019-October/531812.html