Summary: Add the required compiler flag for Folly when building x86_64. I'll prepare a new release for this shortly. Depends on #126 Closes https://github.com/facebook/Sonar/pull/128 Reviewed By: danielbuechele Differential Revision: D8731955 Pulled By: priteshrnandgaonkar fbshipit-source-id: 9511811b0b51205989a5200ad9d0d8689ca684cb