[seL4] RISC-V port

Hi I am trying to build "seL4 tests" for "Spike" platform (the RISC-V simulator from UC Berkeley) on Ubuntu 18.04.3 LTS, a 64-bit system. First of all, I was able to build RISC-V tools with "build.sh" after manually installing "riscv-gnu-toolchain" from GitHub as well as additional python modules (future, ply, protobuf). I then kicked of "../init-build.sh -DPLATFORM=spike -DRISCV64=TRUE -DSIMULATION=1" from local build directory. After that, however, "ninja" command complained about "undefined reference to `__nedf2'". I understand there is no FPU support in "Spike" platform so a need for "soft-float" module. Where should I specify "-lsoft-fp"? Any suggestions? Thanks, Jacob