How to get rid of "_ZL10nimZeroMemPvl" in an embedded target?

[dwhall256]

Ignoring compiled ARM code size for the moment, here's a behavior from the nim 
compiler I don't understand: this gives an error: 
<https://play.nim-lang.org/#ix=4KkD> . Then remove the `#` on line 4 to see it 
build without error.