Run the steps for building libfuzzer-js first.
git clone --depth 1 https://github.com/MikeMcl/bignumber.js.git
export BIGNUMBER_JS_PATH=$(realpath bignumber.js/bignumber.js)
export CXXFLAGS="$CXXFLAGS -DCRYPTOFUZZ_BIGNUMBER_JS"
cd cryptofuzz/modules/bignumber.js/
make