Fix Meson deprecation from Facebook docs
Review Request #1555 — Created July 29, 2022 and submitted — Latest diff uploaded
Fixes this deprecation:
../doc/reference/protocols/facebook/meson.build:25: WARNING: Project targeting '>=0.58.0' but tried to use feature deprecated since '0.56.0': meson.build_root. use meson.project_build_root() or meson.global_build_root() instead.
Reconfigured and saw no warning.