Printf does not work on stock Rocket with htif_wrap.specs

[baltazarortiz]

I tested the minimal stdio wrapper using the shown command ($ riscv64-unknown-elf-gcc -O2 -specs=htif_nano.specs -specs=htif_wrap.specs -o hello tests/hello.c) and ran it on a stock Rocket core (through Chipyard and not just Rocket, if it matters), but did not get any output other than the message saying the UART is ready.

Not super sure how to debug since OpenOCD/GDB is unusably slow for me. Let me know if there is additional info I can provide!