The tests suite calls `diff` in various places, which means we need to
check if it's installed.
installed_test_bindir = join_paths(gtk_libexecdir, 'installed-tests', 'gtk-4.0')
installed_test_datadir = join_paths(gtk_datadir, 'installed-tests', 'gtk-4.0')
+# We call diff in various tests, so we need to check it's available,
+# otherwise we're going to have failures down the line
+diff = find_program('diff', required: true)
+
subdir('gdk')
subdir('gsk')
subdir('gtk')