LPS-43543 Fix SF

Hey Nate, I found a couple of issues on the build-r2-js task after yesterday's reviews.

- I guess you intended to move the `r2_liferay.js` file, but deleted it instead. This is a dependency for portal, and does not come packaged in the zip file. One of the requisites to move away from our fork at some point.

- The output of the `browserify` execution needs to be placed onto the `portal-impl/.../dynamiccss/dependencies` folder, since that's where `RTLCSSUtil.java` is looking for it.

Let me know if you think we could simplify it somehow.

Thanks!