w32_getreg.c needed in build.sh for mingw

From: ANDREW MARLOW, BLOOMBERG/ LONDON OF (amarlow1_at_[hidden])
Date: 2005-06-06 12:17:31

I think that w32_getreg.c needs to be in the
list of source files in build.sh to cater
for minGW. Without it, the link fails due
to unsatisfied references from builtin.c.
w32_getreg.c would have to be an empty
translation unit for POSIX environments,
of course.

Comments?

-Andrew Marlow