Variety’s annual Welcome to Cannes Party started with a bang — literally. A wooden structure that had been erected on the roof of the JW Marriott Cannes began to buckle under the weight of the partygoers, forcing guests to move to another part of the terrace where the champagne flowed and the good times kept rolling, albeit on firmer ground. “Welcome to the most talked-about party at Cannes,” Variety Co-President and Publisher Dea Lawrence said in her introductory remarks. “We appreciate all the strong and the brave in show business who stuck it out and stayed.” And stay they did.…