Unlike the UK the majority of Greece has not large home building contractors, most are small local builders. Even during the current climate the building industry quietly continues. Yes, some people have "frozen" their build, but I believe generally home building continues for the local communities.
This may not apply in relation to holiday homes for ex-pats though.
People in Greece build as money permits, not getting into debt of mortgages etc. Family homes are built over a time period.
Unlike Spain ex-pats also tend in the main not to have mortgages on properties in Greece and if money is not "desperate" will just close the house up rather than sell it at a ridiculously low price.