message: Update build-unix.md
  update build depends
diff: @@ -81,7 +81,7 @@ Build requirements:
  Now, you can either build from self-compiled [depends](/depends/README.md) or install the required dependencies:
  - sudo apt-get install libevent-dev libboost-system-dev libboost-filesystem-dev libboost-test-dev libboost-thread-dev
  + sudo apt-get install libevent-dev libboost-system-dev libboost-filesystem-dev libboost-test-dev libboost-thread-dev libssl-dev
  BerkeleyDB is required for the wallet functionality.
  Historically Peercoin was first deployed with now deprecated BerkeleyDB-4.8, which has resulted in the need to upkeep the compatibility with those ancient deployments to this day. BerkeleyDB-4.8 is not compatible with more modern BerkeleyDB-5.1 and BerkeleyDB-5.3. Peercoin has inherited this in the first versions and this is why Peercoin is still officially shipped out with BerkeleyDB-4.8.
  