In Swiss German I would spell it "glustig" or "gluschdig". I would "germanize" it as "gelustig". If you are "glustig uf öppis" it means you have "Lust darauf", often used in the context of food. "glust" on its own just means "Lust" as in "Gelüste". As explained in the article if you are "glustig" you are not necessarily hungry but you just crave some food. "Ich hab zwar schon gegessen aber irgendwie hab ich voll Lust auf nen Döner!"