Ar71xx unavailable in last image build release

hi there
i have mikrotik rb912 and want to create new custom image build for it but when
i update my image build to new release i didn't get ar71xx target and with ath79 its only have rb921 and 922 board and some sxt and lgh
what is best way to build image for rb912 ??
thx

https://downloads.openwrt.org/releases/19.07.4/targets/ar71xx/mikrotik/ is present for 19.07.4. For master (and the upcoming openwrt-20.xy release branch) the ar71xx target has been removed, any devices missing from the ath79 target will either have to be ported over very soon or they won't have any future support.

thank you for your helpful reply its solved it