Uploading plugins is broken if caching is off

I get errors (`cp org.scala-ide.worksheet/target/site does not exist`) when trying to build a release with caching off. Looks like the issue might be

```
function publishPlugin () {
  info "uploading $1"

  cd "${TMP_DIR}"
  rm -rf *
  P2_ID_VAR_NAME=$3_P2_ID
  cp -r "$(getCacheLocation ${!P2_ID_VAR_NAME})" site
```
