repo init -u https://github.com/nitrogen-project/android_manifest.git -b 11
# Look for your device's local manifest file in this organization's page. In case of oneplus3, that will be oneplus3_local_manifest, so:
git clone https://github.com/nitrogen-project/oneplus_local_manifest.git .repo/local_manifests -b 11
Then to sync up:
repo sync -j$(nproc --all)
Build command is
. build/envsetup.sh
lunch nitrogen_oneplus3-userdebug
make -j$(nproc --all) otapackage