Fill in third-party dependencies for folly

Summary:
I found these by repeatedly running `dotslash-oss ./buck2 targets ...` in the GitHub version of folly after fixing all the non-third-party dependencies (see previous diff).

This works by querying `pkg-config` for the correct pre-processor/linker flags to pass to `cc` for a package installed on the system (by homebrew or whatever).

Reviewed By: namanahuja

Differential Revision: D57384136

fbshipit-source-id: 385218aba98e332bfeea7af7fa2bd53bc194cb8e