How did Meursault change his outlook by the end of the novel? Why did he want to be greeted by cries of hatred?

Meursault's desire to have people scream hatred and abuse at him prior to his execution is a sign that he does, after all, want his life to have had at least some meaning. This represents a major change from the steadfast nihilism he's displayed up until this point. Meursault recognizes that if people greet him with cries of hatred, then it will mean something; it would be an unavoidable expression of righteous anger, and no amount of nihilistic indifference would ever be able to withstand it.
For the first time in his short life, Meursault wants to be part of something that has meaning for him. Killing the Arab was meaningful in itself—but because it happened to someone else, Meursault never really owned its meaning. His forthcoming execution is different, however; this will be his death and no one else's. Everything associated with this death will have meaning for him.
It says something about Meursault's radically existentialist outlook that only his own death can supply his life with meaning.