folly: 2018.06.11.00 -> 2018.06.18.00

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/folly/versions.

These checks were done:

- built on NixOS

- 0 of 0 passed binary check by having a zero exit code.
- 0 of 0 passed binary check by having the new version present in output.
- found 2018.06.18.00 with grep in /nix/store/cbijzsfm1ik0hmblhsg9q8krwq0gs69r-folly-2018.06.18.00
- directory tree listing: https://gist.github.com/d36711520cd03c3b19d6a9f3bc3dc523
- du listing: https://gist.github.com/d83b87211ca6b6a6a538eccba6783c66