First download StrongSwan source code from official site.
Extract source code tarball to directory strongswan/
vim strongswan/configure.ac
Around Line 200:
ARG_ENABL_SET([eap-5g], [enable EAP 5G authentication module.])
Around Line 1480:
ADD_PLUGIN([eap-5g], [c charon nm cmd])
Around Line 1650:
AM_CONDITIONAL(USE_EAP_5G, test x$eap_5g = xtrue)
Around Line 1930:
AM_CONDITIONAL(USE_EAP_5G, test x$eap_5g = xtrue)
cd strongswan/
git clone https://github.com/syujy/strongswan-eap-5g-plugin.git src/libcharon/plugin/eap_5g
autoreconf -i
./configure --prefix=/usr --sysconfdir=/etc --enable-eap-mschapv2 --enable-kernel-libipsec --enable-swanctl --enable-unity --enable-vici --enable-xauth-eap --enable-xauth-noauth --enable-eap-identity --enable-md4 --enable-pem --enable-openssl --enable-pubkey --enable-farp --enable-eap-gtc --enable-eap-5g
make
sudo make install
You can reference this site.