Build failure after interrupted first build

[Vincent Pelletier]

Hi.

I got a failure building wine, where wrc would fail on utils.c:xmalloc's 
"assert(size > 0)". This came from a po/*.mo file being present but empty 
because a first build got interrupted (^C).

Just in case either someone here can figure out a one-liner fix for this, or 
if it helps the next person encountering that behaviour.

Regards,