you want to hold to factory firmware? it is an old version of jeelabs/esp-link. there is the build toolchain documented
I recommend you to change to WiFi Link. There is the upload of new and changed static web files with one click in IDE menu.
The WiFi Link firmware is an Arduino sketch so you can build it in Arduino IDE and upload it to ESP from Arduino IDE. There is no need for some linux toolchains like is the case with other ESP firmwares.
Building WiFi Link firmware from source files gives you possibility to build the newest version, build a branch version, build some fork version or change something in source code you need.
In subfolder data of the source codes of the WiFi Link firmware are the static web files (html, css, js) for the Web Panel. You can add your own files and they will be accessible on expected url. A plugin creates a "ESP8266 Sketch Data upload" command in Tools menu. The tool builds the SPIFFS binary and uploads it to selected port. With network port it will use OTA and it is fast.