Update Dockerfile

Dockerfile

@@ -13,6 +13,6 @@ RUN cd /tmp && \
     tar --bzip2 -xf boost_${BOOST_VERSION_MOD}.tar.bz2 && \
     cd boost_${BOOST_VERSION_MOD} && \
     ./bootstrap.sh --prefix=/usr/local && \
-    echo "using mpi ;" >> project-config.jam
+    echo "using mpi ;" >> project-config.jam && \
     ./b2 install && \
     rm -rf /tmp/*