Disable autosetting of optimization flags by libffi. (#8996)

  - Disable the setting of optimization flags. automatically by libffi's
    own decisions. For OpenModelica we want to pass the options and flags
    ourselves.

    This was ignoring all CFLAGS we pass to libffi including `-fPIC`
    breaking the build of OpenModelica on Fedora 36 because the libray
    could not be linked to a shared library (since it was not compiled as
    position independent code.)