How to evaluate my fuzzer in Magma without fetch.sh?

After reading the issue of #171 ,I Started to try my own fuzzer in Magma.
Surprisingly, I got a "[0mThe command '/bin/sh -c ${FUZZER}/fetch.sh && ${FUZZER}/build.sh' returned a non-zero code: 127"
but as mentioned in #171, maybe I can build my fuzzer with local file(without fetch.sh), how could I realize that?
for that if the fetch.sh is not there, the build campain seems not complete.