I don’t recall seeing this error before. But a couple of things may be related:
1. As I said, you should delete ‘test’ or ‘tests’ folders in all relevant libraries, such as pubsubclient. I find them sometimes lead to compilation errors.
2. This step you described:
git clone https://github.com/esp8266/Arduino.git
#Puts it in ~/Arduino
I am not sure where this is coming from — you clone ESP core again into ~/esp8266_2.5.2 in the next step, so why duplicate the core into ~/Arduino? In the error messages you received, there is this line:
“Arduino/libraries/ESP8266WiFi/src/WiFiClientSecureBearSSL.h”
it implies that the compiler is looking for ESP8266 core files in ~/Arduino/libraries folder. This is bizarre, it should be looking for that in ~/esp8266_2.5.2 since that’s what you set as ESP_ROOT in the Makefile.