Multiple arguments for the same option - aggragation broken.

Options who's value is a list can optionally be specified multiple times, so that :
  --java-options "-server -ea -Dfoo=bar"
is the same as
  --java-options -server --java-options "--ea -Dfoo=bar"
or
  --java-options -server --java-options -ea --java-options -Dfoo=bar

This is broken for --add-modules:
  "--add-modules me.mymodule,other.mod"
works fine, but:
  "--add-modules me.mymodule --add-modules other.mod"
results in error message:
"Module [me.mymodule

other.mod] does not exist."

Clearly this is a simple bug where wrong delimiter is used when aggregating these two options, but we need to check all options that are allowed to be aggragated.