I had the same error as you. You need to install gnutls.
I found a how-to here : https://gist.github.com/morgant/1753095
This complete list of commands worked for me (OSX 10.6) :
cd ~/Desktop
mkdir wget-build
cd wget-build
curl -O ftp://ftp.gmplib.org/pub/gmp-5.0.2/gmp-5.0.2.tar.bz2
tar xjf gmp-5.0.2.tar.bz2
pushd gmp-5.0.2
CC=gcc-4.2 CXX=g++4.2 ./configure --prefix=/usr/local
make
sudo make install
popd
curl -O http://www.lysator.liu.se/~nisse/archive/nettle-2.4.tar.gz
tar xzf nettle-2.4.tar.gz
pushd nettle-2.4
CFLAGS="-m64" ./configure --prefix=/usr/local --disable-assembler
make
sudo make install
popd
curl -O http://ftp.gnu.org/gnu/gnutls/gnutls-2.12.12.tar.bz2
tar xjf gnutls-2.12.12.tar.bz2
pushd gnutls-2.12.12
CFLAGS="-m64" CXXFLAGS="-m64" ./configure --prefix=/usr/local --without-p11-kit
make
sudo make install
popd
You could also try to use Brew (http://brew.sh/) and install gnutls via :
brew install gnutls
Finally a third way that worked for me :
curl -O http://libav.org/releases/libav-10.1.tar.gz
tar xjf libav-10.1.tar.gz
cd libav-10.1
./configure
make install
Enjoy !