Update to glib 2.62.6 and iOS / Android fixes

commit f23e0260:

glib.recipe: Bump to 2.62.6

commit c416c27d:

glib.recipe: iOS build fixes
Sync the host_system == ios change with upstream, and don't look for
`_NSGetEnviron()` on iOS. This regressed when moving to Meson since it
was set via `ac_cv_func__NSGetEnviron` in `ios.config` and was missed.

commit c191e4c2:

config: Remove glib-specific autoconf hacks
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