Whether or not you eat what McDonald’s serves, let’s at least agree the fast-food giant has a knack for putting together unexpected ingredients in a way that no one had seen before. The same could be said about “The Founder,” the biographical film about Ray A. Kroc (played by Michael Keaton), the onetime milkshake-machine salesman who helped transform McDonald’s from a roadside stand in San Bernardino, Calif., to an empire of golden arches. The movie (in wide release Jan. 20) also stars Nick Offerman and John Carroll Lynch as Richard and Maurice McDonald, the brothers (known as Dick and Mac) who created the namesake restaurants and invented the rapid-service system, then entered into an uneasy partnership with Kroc, who took over the company. If Kroc is the go-go-go engine of “The Founder,” then the McDonald brothers are its heart — the loyal siblings whose ingenuity and traditional values are eventually overwhelmed by their new partner’s relentless hustle. More