[gtkmm 4.0.0] missing #include <optional> in \untracked\gtk\gtkmm\expressionwatch.h
Tried building gtkmm 4.0.0 with meson using msvc and it complaint about optional not being defined. add #include fixed it.
Tried building gtkmm 4.0.0 with meson using msvc and it complaint about optional not being defined. add #include fixed it.