FIX: builds/ should be the default output directory for rsc.r
FIX: builds/ should be the default output directory for rsc.r

The earlier relative path handling fix introduced a regression by always
building to the current directory, even if no explicit output path was
given. However, Red/System should build to its local builds/ directory,
unless told otherwise. So this fix now only uses the working
directory-relative path logic when given an explicit output path as
command-line option.

NikolayShubenkovProgSchool/red,red-eco/red,iArnold/red,NikolayShubenkovProgSchool/red,iArnold/red,red-eco/red,vehar/red,vehar/red,rheber/red,rheber/red