Revert "super thin standalone groovy 1.8.6 runner"

This reverts commit a47aff05c175905b47829555e413c6cfa7b019e3.
tiny 12k gradlew like groovy 1.8.6 wrapper/runner

This jar is executable (script files optional, but generated if missing
for convenience).  This jar uses ivy 2.2 behind the scenes to install
the groovy 1.8.6 runtime into the ivy cache.