If you have downloaded darktable-fuji-styles.tar.xz and check its Makefile, you may wonder where the referenced tool darktable-lut is located.
It turns out that there is no darktable-lut to be found.
Instead, you are supposed to invoke darktable-chart (which normally resides in the bin section of your installation folder tree).
In my case (compiling my darktable from GitHub), all I have to do is to change the first line in the darktable-fuji-styles Makefile to read TOOL=/opt/darktable/bin/darktable-chart