Images are built using bitbake and yocto.

The build process is based on this toradex guide .

A custom application can be added to a yocto build by means of a new recipes and a new layer.

https://blog.mbedded.ninja/programming/embedded-linux/yocto-project/adding-a-custom-app-to-a-yocto-build/

https://wiki.yoctoproject.org/wiki/Building_your_own_recipes_from_first_principles

To build the SDK for an image append -c populate_sdk to the bitbake build command.

For example, to build the SDK for the standard toradex image console-tdx-image run bitbake console-tdx-image -c populate_sdk

For more information check the Toradex guide .