For historical reasons g_qsort_with_data() "only" works with up to 2**31
items, so it won't necessarily work for pathologically large arrays
and therefore is deprecated.
One advantage of g_qsort_with_data() and its replacement g_sort_array()
is that GLib guarantees that they are a stable sort (will not permute
items that already compare equal), which is not a guarantee for glibc's
qsort() and qsort_r(). However, I don't think it's actually relevant
whether we are doing a stable sort in any of these places: most of the
time we are sorting an array of unique items (often the keys of a hash
table, which are necessarily unique), therefore the compare function
will not compare equal in any case.
Another advantage of the GLib functions is that they are portable,
unlike qsort_r(). However, Flatpak is Linux-only, so we can freely use
useful functions like qsort_r().
Signed-off-by: Simon McVittie <smcv@collabora.com>