flatbuffers: 1.8.0 -> 1.10.0 (#48521)

* flatbuffers: 1.8.0 -> 1.10.0

Semi-automatic update generated by
https://github.com/ryantm/nixpkgs-update tools. This update was made
based on information from
https://repology.org/metapackage/flatbuffers/versions

* flatbuffers: fix build on Darwin and enable checks

Bazel BUILD file is conflicting with build directory on case-insensitive FS
+ checkPhase now runs "make test"