while cross building is technically possible, it will require you to hack up your host system a lot to teach it to fully support arm64 packages first …
then you need to have a cross compiler and need to patch the build systems of all the sources you build to make sure they understand cross compiling if they do not already … and indeed all your compiler environment variables need to be adjusted to point to the right places …
if you can not do your build with https://snapcraft.io/build or use snapcrafts remote-build feature:
i’d really recommend getting arm64 hardware to build on … cross building anything that has actual library dependencies is extremely painful and fragile …