These haven't been used ever since glib was ported to Meson:

glib_cv_stack_grows is now set as a cross property
glib_cv_uscore is correctly detected with meson
getpwuid_r is correctly detected with meson
getgrgid_r is correctly detected with meson
wchar_t is available and things work fine (added in 2013, no notes)
_NSGetEnviron is fixed in the previous commit

Part-of: <gstreamer/cerbero!489>