How to build openssh with support for FIDO Security keys on Ubuntu 18.04

install-openssh-sk.sh

sudo apt update
sudo apt install -y cmake cmake-data pkgconf autoconf
sudo apt install -y libssl-dev libudev-dev libcbor-dev libz-dev

git clone https://github.com/Yubico/libfido2.git
cd libfido2/
mkdir build
(cd build && cmake ..)
make -C build
sudo make -C build install
cd -

git clone https://github.com/openssh/openssh-portable.git
cd openssh-portable/
autoreconf
./configure
make
# skipping install for now 
cd -

export SSH_SK_PROVIDER=/usr/local/lib/libsk-libfido2.so

# server:
echo "AuthorizedKeysFile .ssh/authorized_keys" > ./sshd_config
ssh-keygen -t ecdsa -C"hostkey" -f ./host_ecdsa
${PWD}/openssh-portable/sshd -h ${PWD}/host_ecdsa -d -e -p 22222 -f ${PWD}/sshd_config

# client
./openssh-portable/ssh-keygen -t ecdsa-sk -f id_ecdsa_sk
# add client public key in id_ecdsa_sk.pub to  ~/.ssh/authorized_keys on server
./openssh-portable/ssh  -F /dev/null -p 22222 localhost -i id_ecdsa_sk