OOM debug option: simplify its management and make it compatible with arduino-1.9beta

[d-a-v]

The gcc option -include "..." is broken with arduino-1.9 and was finally not mandatory for oom debug anywhere in its final version.
Tested with arduino 1.8 and 1.9.

This simple sketch

#include <ESP8266WiFi.h>

void setup()
{
  Serial.begin(115200);
  Serial.setDebugOutput(true);

  Serial.println(ESP.getFreeHeap());
  Serial.println((int)malloc(ESP.getFreeHeap() - 300), HEX);
  Serial.println(ESP.getFreeHeap());
  Serial.println((int)malloc(400), HEX);
  Serial.println(ESP.getFreeHeap());

  WiFi.begin("open", "");
}

void loop()
{
}

still shows:

16:05:21.670 -> 46792
16:05:21.670 -> 3FFF0944
16:05:21.670 -> 280
16:05:21.670 -> :oom(400)@/home/gauchard/dev/proj/arduino/oom/oom.ino:11
16:05:21.670 -> 0
16:05:21.670 -> 280
16:05:21.670 -> :oom(1176)@user_interface.c:2248
16:05:21.670 -> :oom(1176)@user_interface.c:2248
16:05:21.670 -> :oom(1176)@user_interface.c:2438
16:05:23.792 -> scandone
16:05:23.792 -> state: 0 -> 2 (b0)
16:05:23.825 -> state: 2 -> 3 (0)
16:05:23.825 -> :oom(208)@esf_buf.c:351
16:05:23.825 -> Fatal exception 29(StoreProhibitedCause):
...

[devyte]

I don't feel competent to review this (I don't understand the code changes). However, if 1.9 solves the rebuild all issues, then all preparations to move to it are welcome!

[electron1979]

IDE 1.8.7 Stable seems to be fine, too.