This is the simplest but also least useful way to build packages for yocto. By default, there is no toolchain installed in the image.
To add the toolchain to an image, append tools-sdk to CORE_IMAGE_INSTALL.
dunfell and earlier:
CORE_IMAGE_INSTALL_append = " tools-sdk"
honister and later (namely kirkstone):
CORE_IMAGE_INSTALL:append = " tools-sdk"
Note that this will significantly increase image size and build time.