This complements the `--glib-min-required` argument, just like the
`GLIB_MIN_REQUIRED` and `GLIB_MAX_ALLOWED` preprocessor defines which
control access to APIs in C.
Currently, it doesn’t affect code generation at all. When we next change
code generation, we will need to gate any new API usage on this
argument.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Fixes: #1993