_CRT_SECURE_NO_WARNINGS and _CRT_NONSTDC_NO_WARNINGS not defined for clang-cl

_CRT_SECURE_NO_WARNINGS and _CRT_NONSTDC_NO_WARNINGS are defined in msvc_recommended_pragmas.h. But that file is included only if the compiler is msvc: https://gitlab.gnome.org/GNOME/glib/-/blob/master/meson.build#L22-23

Not sure about the rest of the file (maybe properly enabling G_GNUC_UNUSED and similar things will make them unnecessary), but _CRT_SECURE_NO_WARNINGS and _CRT_NONSTDC_NO_WARNINGS are necessary on clang-cl too.