Add boost to the building from source for macos doc instruction (va…

…lhalla#4830)

docs/docs/building.md

@@ -79,7 +79,7 @@ To install Valhalla on macOS, you need to install its dependencies with [Homebre
 
 ```bash
 # install dependencies (automake & czmq are required by prime_server)
-brew install automake cmake libtool protobuf-c libspatialite pkg-config sqlite3 jq curl wget czmq lz4 spatialite-tools unzip luajit
+brew install automake cmake libtool protobuf-c libspatialite pkg-config sqlite3 jq curl wget czmq lz4 spatialite-tools unzip luajit boost
 # following packages are needed for running Linux compatible scripts
 brew install bash coreutils binutils
 # Update your PATH env variable to include /usr/local/opt/binutils/bin:/usr/local/opt/coreutils/libexec/gnubin