debian buster aarch64/armv7l emulation (on x86_64) - llvm-9, clang-9

docker pull arm64v8/debian:buster
or
docker pull pinto0309/raspios_lite_armhf:2021-03-04_buster

docker run --rm --privileged multiarch/qemu-user-static --reset -p yes

docker run --rm -it \
-v ${PWD}:/workdir \
arm64v8/debian \
/bin/bash

docker run --rm -it \
-v ${PWD}:/workdir \
pinto0309/raspios_lite_armhf:2021-03-04_buster \
/bin/bash

cd /workdir

apt update && \
apt install -y wget zip make python3-pip \
git curl lsb-release software-properties-common nano

ln -s /usr/bin/python3 /usr/bin/python
ln -s /usr/bin/pip3 /usr/bin/pip
pip3 install pip --upgrade
pip install gdown numpy==1.21.4 cmake

wget https://github.com/llvm/llvm-project/releases/download/llvmorg-9.0.1/clang-9.0.1.src.tar.xz
wget https://github.com/llvm/llvm-project/releases/download/llvmorg-9.0.1/llvm-9.0.1.src.tar.xz

tar -xf clang-9.0.1.src.tar.xz
tar -xf llvm-9.0.1.src.tar.xz

mv llvm-9.0.1.src llvm9
mv clang-9.0.1.src clang

cd llvm9 && mkdir build && cd build
cmake -DLLVM_ENABLE_PROJECTS=clang -G "Unix Makefiles" ../
make -j$(nproc)
make install