Please check, correct if necessary and apply the attached diff (named cc.diff) to allow code coverage. Currently it supports only dynamic instrumentation.
Also diff contains a fix to allow redefine setting by local properties ${user.home}/.nashorn.project.local.properties (it needs to simplify automation execution of custom machines)
 
Code coverage is disabled by default
to enable it redefine in the ${user.home}/.nashorn.project.local.properties
parameter
make.code.coverage=true
and check that jcov2.lib.dir points to correct location (default value is upper directory of nashorn project - jcov2.lib.dir=${basedir}/../jcov2/lib)

redefine if necessary, like
jcov2.lib.dir=/opt/jcov2/lib