Like most films made in Hollywood, Blazing Saddles (a Warner Brothers' production) was intended to appeal to the largest audience possible – or at least, the largest adult audience possible, given its R rating. It's reasonable to assume that it wasn't explicitly made for black audiences. The "blacksploitation" films that were concurrent with Blazing Saddles tended to be set in predominantly African American milieux, which this film is not. However, as I said, not only were black viewers part of the "general audience" that Hollywood aspired to reach, but it's likely that the producers would assume that having a (more or less sympathetic) black protagonist would bring in a wider share of the black audience, even at the risk of alienating some portion (read: racists) of the white audience. (I think those folks probably weren't into borscht belt comedy anyway, though.) Rick Altman's book Film / Genre is a good introduction to the polyvalent appeals of Hollywood productions.

It hardly represents a critical consensus, but writing decades later in Toms, Coons, Mammies, Mullatoes, and Bucks, Donald Bogle speaks approvingly of the film's presentation of a "new-style coon*: a coon with a double consciousness." He attributes the much of the film's success as comedy and racial text to Richard Pryor's role as screenwriter; he was apparently initially planned to star, too.

*Yes, this is a racial epitaph, but Bogle recasts it as a critical term in the racial economy he sketches in Hollywood.