The derefnull and divbyzero tests appear to fail non-deterministically on Windows (e.g. this job), exiting with code 127:

cd "rts/divbyzero.run" && ./divbyzero   < 
Wrong exit code for divbyzero(normal)(expected 8 , actual 127 )
*** unexpected failure for divbyzero(normal)

I haven't been able to reproduce this locally, but Phyx has under WinDbg. It may also be more likely to occur under PowerShell then Conemu.