These don’t show up for me on Linux, but are now causing CI failures on
macOS (https://gitlab.gnome.org/GNOME/glib/-/jobs/5006543):
```
../gobject/gclosure.c:923:40: error: implicit conversion changes signedness: 'gboolean' (aka 'int') to 'guint' (aka 'unsigned int') [-Werror,-Wsign-conversion]
ATOMIC_SET (closure, in_marshal, in_marshal);
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
```
Signed-off-by: Philip Withnall <pwithnall@gnome.org>