Prebuilt Android NDK for host android-aarch64.
curl https://storage.googleapis.com/git-repo-downloads/repo > /usr/bin/repo
chmod 755 /usr/bin/repo
mkdir llvm-toolchain && cd llvm-toolchain
repo init -u https://android.googlesource.com/platform/manifest -b llvm-toolchain
cp ../manifest_7714059.xml .repo/manifests
repo init -m manifest_7714059.xml
repo sync -c -j$(($(nproc --all)+1))
python toolchain/llvm_android/build.py --build-name 7714059 --no-build windows --skip stage1