I have not installed nukes but it looks like the tag is not replaced by ant.
search the ant file for this token and see if the value has been declared.
this property is located in $nukes/build/etc/local.properties-xxx
where xxx = mysql ou hsqldb
when you first execute $nukes/build/build.xml by doing
sh build.sh or build.bat, it copies the hsqldb one, it setup properties
for the build.
so if it fails (I dunno why) you can copy one of these files according the db you want to use in $nukes/build as local.properties.