Update LESS_BINARY and add BABEL_BINARY to cope with no symlinks.
Update LESS_BINARY and add BABEL_BINARY to cope with no symlinks.

Vagrant on windows has issues creating symlinks, especially from within
`npm install`. It's possible to use `npm install --no-bin-links`, but then
things are not included in `node_modules/.bin`. People have also hit similar
issues on other platforms due to the .bin directory not being part of their
`$PATH`.

This change explicitly references the right scripts inside the `less` and
`babel-cli` modules, so we no longer need to rely on the contents of the .bin
directory.

Testing done:
Verified that compilation still worked.

Reviewed at https://reviews.reviewboard.org/r/7994/

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