filter_geoip2: enable gnu99 mode to build dependency
# Please update the content when you upgrade libmaxminddb.
#
option(BUILD_TESTING "" OFF)
+set(CMAKE_C_FLAGS "-std=gnu99 ${CMAKE_C_FLAGS}")
add_subdirectory(libmaxminddb EXCLUDE_FROM_ALL)
include_directories(libmaxminddb/include/)
