Building a package was failing due to reviews.less attempting to

reference a Djblets .less file. This wasn't working for two reasons.
First, STATIC_ROOT was undefined during packaging, preventing this path

from working at all.
Second, Djblets's static media files were not in the include path,

making it impossible for the referenced files to be found during

packaging.
To fix this, our static media builder script now defines some arguments

to pass to lessc that set the include path and provides some global

variables. This is similar to what's set for packaged extensions, though

is a subset of only the data needed by Review Board's own .less files.

Successfully built a package.