To get started with building LineageOS GSI, you'll need to get familiar with Git and Repo, and set up your environment by referring to LineageOS Wiki (mainly "Install the build packages") and How to build a GSI.
First, open a new Terminal window, create a new working directory for your LineageOS build (leaos for example) and navigate to it:
mkdir leaos; cd leaos
Initialize your LineageOS workspace:
repo init -u https://github.com/LineageOS/android.git -b lineage-20.0 --git-lfs
Clone both this and the patches repos:
git clone https://github.com/iceows/lineage_build_leaos lineage_build_leaos -b lineage-20.0
git clone https://github.com/iceows/lineage_patches_leaos lineage_patches_leaos -b lineage-20.0
Finally, start the build script (64VN = Vanilia / 64GN = GoogleApps):
bash lineage_build_leaos/build.sh treble 64VN
Be sure to update the cloned repos from time to time!
EMUI 9 or EMUI 10 targets for Huawei re generated from AB images instead of source-built - refer to huawei-creator.
This script is also used to make builds without sync repo. To do so add nosync in the command build line.
bash lineage_build_leaos/build.sh treble nosync 64VN
bash lineage_build_leaos/build.sh device anne