Initialize repo:
repo init -u git://github.com/lj50036/platform_manifest_twrp_omni.git -b twrp-5.1
curl --create-dirs -L -o .repo/local_manifests/pop35.xml -O -L https://raw.githubusercontent.com/zombah/twrp_local_manifest/twrp-5.1/pop35.xml
repo sync
source ./build/envsetup.sh
lunch omni_pop35-userdebug
make recoveryimage