move -Wextra-semi to GCC 8.0+
move -Wextra-semi to GCC 8.0+

alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,google/flatbuffers,google/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,google/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,google/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,google/flatbuffers