was a good tip. (How can somebody know such special things...)
Made this changes in the Makefile:
-- CFLAGS ?= -std=gnu99 -Os -Wall
++ CFLAGS ?= -std=gnu99 -Os -Wall -mno-ms-bitfields
Then compiling the mkspiffs.exe
Your (martinayotte) image with the new one:
C:\ArduinoEsp8266>mkspiffs -l spiffstest_martin.bin
1405 /metalic.png
1428 /Tourlou.txt
1428 /README.md
Then making my own image -> flashing to ESP -> directory strucure is OK, content of the file is OK.
How to tell igrr to change the Makefile for windows? And modify the spiffs_config.h
ESP8266 Arduino add-on
Arduino IDE 1.6.5