download from github:
git clone https://github.com/friendlyarm/prebuilts.git -b master --depth 1
or download from gitee:
git clone https://gitee.com/friendlyelec/prebuilts.git -b master --depth 1
and then:
cd prebuilts/gcc-x64
cat toolchain-4.9.3-armhf.tar.gz* | sudo tar xz -C /
cat toolchain-6.4-aarch64.tar.gz* | sudo tar xz -C /