I am trying to use CoqMakefile to automatically build my Coq project in Coq 8.15.2. When I did this the compilation failed because a file ".CoqMakefile.d" was expected by make but did not exists and make did not know how to produce it. This problem occured on two different computers with two different operating systems.
Weirdly, creating an empty file with this name solved the issue and make now runs without a problem. Even more weirdly, deleting the file again did not cause a problem: Now make is able to automatically generate it.
I am puzzled. What is going on here? What is the job of .CoqMakefile.d? Why could it not be generated by the automatically generated CoqMakefile? And why can it be generated once it has existed once?