Based on the M_CLI2 documentation, it is possible to have a compound response file whose name should be EXEC.rsp where EXEC is the name of the executable. When using a response file in a package using FPM for its compilation, the EXEC is indeed the name of the FPM binary not the executable of the package. There are a couple of packages on github with the response file named fpm.rsp, this means the name of the binary of FPM must be fpm or a soft link whose name is fpm.
Those, who download the binary of FPM from github, should pay attention to this point.