Jonas Dreßler authored Dec 30, 2021 and Rico Tzschichholz committed Jan 03, 2022

It seems that with gtk commit c4d350c260879c11ea94641ac820b331aeaccc7c,
the quartz backend option got removed and replaced with the newer
macos-backend option.

Meson complains about unknown options, which broke the gtk4 build, so
fix that by using the macos-backend build option for gtk when the quartz
condition is set.