Why build script forces to download boost dependency?

Why it doesn't offers an option to use installed one? 'boost_1_62_0.tar.bz2' is 81 MB large, it is downloaded with 'wget' and if something goes wrong it brakes the building process. I even have no an option to substitute predownloaded 'bz2' to skip downloading it each time I start building after fail.

It seems workaround is to copy downloaded file to the target dir of the 'test' command.