You may wish to install Linaro cross-toolchains manually. If you look here there are binary releases:
[url]https://releases.linaro.org/components/toolchain/binaries/[/url]
You’re probably intersted in a combination of aarch64-linux-gnu and armv8l-linux-gnueabihf (or possibly arm-linux-gnueabihf ). The 64-bit aarch64/arm64 has a compatibility mode…if you do not build kernels you will not need anything 32-bit (gnueabihf is 32-bit). I do not know what Qt will require.
Consider cloning the rootfs partition of your Jetson if you run into complicated sysroot needs (think of files you need to link to being made available on your host). Cloning explained here (there is a patch listed for flash.sh):
[url]https://devtalk.nvidia.com/default/topic/1000105/jetson-tx2/tx2-cloning/[/url]