Simplify Gradle dist task
Simplify Gradle dist task

Since tar.gz dist package is no longer produced, the dist task can directly handle
ZIP generation.

dita-ot/dita-ot,dita-ot/dita-ot,shaneataylor/dita-ot,drmacro/dita-ot,shaneataylor/dita-ot,shaneataylor/dita-ot,infotexture/dita-ot,drmacro/dita-ot,shaneataylor/dita-ot,dita-ot/dita-ot,drmacro/dita-ot,infotexture/dita-ot,drmacro/dita-ot,dita-ot/dita-ot,infotexture/dita-ot,infotexture/dita-ot,infotexture/dita-ot,drmacro/dita-ot,dita-ot/dita-ot,shaneataylor/dita-ot