add flatbuffers dep

.gitmodules

@@ -16,3 +16,6 @@
 [submodule "deps/json"]
 	path = deps/json
 	url = https://github.com/nlohmann/json.git
+[submodule "deps/flatbuffers"]
+	path = deps/flatbuffers
+	url = https://github.com/google/flatbuffers.git

build_deps.sh

@@ -18,6 +18,14 @@ done
 rm -rf ${DEPS_INSTALL_PATH}
 mkdir -p ${DEPS_INSTALL_PATH}
 
+# Build flatbuffers
+cd $BASE_DIR/deps/flatbuffers && rm -rf build && mkdir -p build && cd build && \
+  cmake -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DFLATBUFFERS_BUILD_TESTS=OFF -DCMAKE_CXX_STANDARD=11 \
+        -DFLATBUFFERS_STATIC_FLATC=OFF -DFLATBUFFERS_BUILD_FLATHASH=OFF \
+        -DCMAKE_INSTALL_PREFIX=${DEPS_INSTALL_PATH} .. && \
+  make -j$(nproc) install && \
+  rm -rf $BASE_DIR/deps/flatbuffers/build
+
 # Build yaml-cpp
 cd $BASE_DIR/deps/yaml-cpp && rm -rf build && mkdir -p build && cd build && \
   cmake -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DYAML_CPP_BUILD_TESTS=OFF -DCMAKE_CXX_STANDARD=11 \