how to manage %files section in spec without environment variables

I am creating a package for a software using MPICH. The binaries must be installed on the [mpich directory](https://docs.fedoraproject.org/en-US/packaging-guidelines/MPI/) . This directory depends on the mpich version (/usr/lib64/mpich-3.2/ or /usr/lib64/mpich/). For the %install section, I managed with variables MPI_BIN and MPI_LIB setting by macro. But these variables are not expanded in the %files section. How can I list the binaries in the %files section ? I have read an [old post](https://unix.stackexchange.com/questions/6601/spec-files-attribute-and-shell-variables) but the solution doesn't work.