QEMU doesn't support the RTC peripheral yet so work around it for now.
This makes the following command work:
tinygo run -target=hifive1-qemu ./testdata/coroutines.go
See the following bug: https://bugs.llvm.org/show_bug.cgi?id=42881
I think this is a bug in LLVM, but the code in question wasn't the best
code anyway. By fixing this, about 16 bytes of code are saved on ARM
chips (and much more on AVR).