Enable link_input_files in projects/release/config

After the patch for rbm#40025 (closed) is merged, we should set link_input_files to 1 in projects/release/config.

This should allow us to have files from {alpha|release}/unsigned/$version as hard links to the files in out/tor-browser/, saving a few GBs of disk space for each release build, and making the build a little faster.