What did you call "Embedded linux"?
Are you sure gtk is available on your target?
If you say "Embedded linux" as a minimal linux tailored for your needs, there's no miracle, you have to know how works linux: boot, init scripts, bash (or other shell) programming, filesystem organization (/dev, /proc, /sys, /etc...), kernel compilation, and so on... And when you have understood how all of theses work all together, you can do your own linux system by hand very easily.
There's another thing to care about, does the development arch is the same that the target arch? If not, you have to use a cross-toolchain, which is another difficulty.
Depending on what's your target, you can find "all in one" development environment (to create a system by menu driven application, a a target designed compiler), for exemple I'm using linux on Analog Device blackfin DSP, and you can found all necessary stuff at blackfin.uclinux.org which just work "out of the box"...