Small improvements to the vagrant build for centos

Fix provided by @akon-dey
Closes: #780

vagrant/centos/vagrant-build-gpdb.sh

@@ -15,7 +15,7 @@ export PATH=/usr/local/bin:$PATH
 
 rm -rf /usr/local/gpdb
 pushd ~/gpdb
-  ./configure --prefix=/usr/local/gpdb $1 
+  ./configure --prefix=/usr/local/gpdb $@
   make clean
   make -j4 -s && make install
 popd
@@ -23,9 +23,8 @@ popd
 # generate ssh key to avoid typing password all the time during gpdemo make
 rm -f ~/.ssh/id_rsa
 rm -f ~/.ssh/id_rsa.pub
-rm -f ~/.ssh/authorized_keys
 ssh-keygen -t rsa -N "" -f "$HOME/.ssh/id_rsa"
-cat ~/.ssh/id_rsa.pub > ~/.ssh/authorized_keys
+cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
 chmod 600 ~/.ssh/authorized_keys
 
 # BUG: fix the LD_LIBRARY_PATH to find installed GPOPT libraries

vagrant/centos/vagrant-setup.sh

@@ -18,6 +18,7 @@ sudo yum -y install epel-release
 sudo yum -y install htop
 sudo yum -y install perl-Env
 sudo yum -y install ccache
+sudo yum -y install libffi-devel
 wget https://bootstrap.pypa.io/get-pip.py
 sudo python get-pip.py
 sudo pip install psutil lockfile paramiko setuptools epydoc