Fixed small typo

doc/bulding-on-ubuntu-debian.md

@@ -6,7 +6,7 @@
 1. sudo apt-get install build-essential libssl-dev libboost-all-dev libdb++-dev libminiupnpc-dev git openssl
 1. git clone https://github.com/miguelfreitas/twister-core.git
 1. cd twister-core/libtorrent
-1. ./bootstrap.sh —with-boost-libdir=/usr/lib/x86_64-linux-gnu
+1. ./bootstrap.sh --with-boost-libdir=/usr/lib/x86_64-linux-gnu
 1. ./configure --enable-logging --enable-debug --enable-dht
 1. cd ../src
 1. make -f makefile.unix