Download and unpack
git clone https://github.com/caviumnetworks/thunderx-tools.git
cd thunderx-tools/thunderx-tools-421/
sh ./unpack.sh
Add aarch64-thunderx-linux-gnu-gcc to system path
THUNDERX_TOOLS=/path/to/thunderx-tools-421
PATH=${THUNDERX_TOOLS}/bin:${THUNDERX_TOOLS}/usr/bin:$PATH