When vk_require_astc is true and there is no native ASTC LDR support, enable ASTC LDR emulation. vk_require_astc defaults to true on Android 14+. Signed-off-by: Chia-I Wu <olvaffe@gmail.com> Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25467>