run gn gen
against the Fuchsia build directories.
Execute a `gn gen` against the Fuchsia build If successful, execute a `gn gen` against the Fuchsia build. In abstract, if FUCHSIA_BUILD_DIR is out/x64, this is simply: gn gen out/x64 It is useful if one has by some mechanism deleted the ninja artifacts, but not the args.gn, e.g. if one CTRL+C's a regen step (gn bug).