the way to do:
- repo init -u git://github.com/minimal-manifest-twrp/platform_manifest_twrp_omni.git -b twrp-6.0
- repo sync
- git clone https://github.com/h0sch180/android_twrp_device_jiayu_s3 device/jiayu/s3_h560
- . build/envsetup.sh
- lunch omni_s3_h560-eng
- make -j# recoveryimage [# : no. of cpu core]