I finally found out how to proceed, I explain it for those who are interested :
You just have to follow the explanation number 3) of Giuseppe Guerrini on this thread with few modifications :
For b) I saved the script as linker_temp.c (you can either save it as linker_temp.ld)
For 3) c) go to Project > Properties > C/C++ Build > Settings > Build Steps and write the following command on Pre-build steps > Command :
arm-none-eabi-gcc -P -E ..\linker_temp.c -o ..\STM32F411RETx_FLASH.ld
See the picture attached.
Change the name of your input and output file (linker_temp.c and STM32F411RETx_FLASH.ld for me) according to your project.
And pay attention to the path of each file, even inside the linker_temp file when including your header file.