Bronx cheer is the same as the British raspberry, isn't it.

AFAIK. It is sometimes called a voiced linguolabial trill /r̼/. Raspberry is Cockney rhyming slang for fart: raspberry tart. It doesn't seem to be used in any languages phonemically, but it does occur in Coatlán Zapotec (link, p.5.) in sound symbolism.

Ceci n'est pas un seing.