[Bug c++/98646] [11 Regression] A static_cast confuses -Wnonnull, causing false positives

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98646

--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Or, disable it when we call build_base_path with nonnull == 1?