HTIF tohost symbol size check always fails

[Peer Adelt]

Hi,

I have a problem with the RISC-V HTIF device. 

Every binary I have compiled for Spike on riscv32 fails with the following 
error message: "HTIF tohost must be 8 bytes"

This happens regardless of which program I have translated for Spike. This is 
also the case with the official riscv-compliance tests, for example.

The query "if (st_size != 8)" in the HTIF device always fails, because st_size 
seems to be always 0.

To be able to reproduce it:
- QEMU GIT Hash: d0ed6a69d399ae193959225cdeaa9382746c91cc (tag "v5.1.0")
- System: Mac OS 10.14.6 (Darwin Kernel Version 18.7.0)
- Compiler: Latest SiFive Build for GCC under OSX
- Command: qemu-system-riscv32 -M spike -nographic -bios none -kernel 
<ANY_SPIKE_ELF_FILE>

Best regards,
Peer Adelt