Build the tool chain image. It generates the toolchain that will be installed on your host machine and used to build any source code:
$ bitbake meta-toolchain
It does take some time to build.
Why to create a toolchain?
Yocto is not intended to be used to package development. Yocto is a linux distribution creator. It´s intended to be a image builder, a rootfs creator. (please, see more about "what is yocto" here and here)
So, yocto itself should not be used to "develop" a new package. Although, Yocto can help creating a environment for development like meta-toolchain or Eclipse ADT.