Fix: arduino platform build

[shuai132]

#if defined(ARDUINO) && !defined(ARDUINOSTL_M_H)

It will case comiple error(I'm using ESP32 and ESP8266 with Arduino SDK):

include/flatbuffers/base.h:36:12: fatal error: utility.h: No such file or directory

I have already read the issue: #4357 and I think it should only apply to AVR.

Because:

#include <utility>

this include is allowed on most platform(even mcu toolchains), e.g: esp32/esp8266/stm32. and arduino framework is works too.

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