README: add how to build

README.md

@@ -7,3 +7,23 @@
 See ./osmo-epdg for a full example configuration (both UE and ePDG).
 
 The ePDG must use the address 192.168.0.2
+
+## how to build
+
+```
+apt install libosmocore-dev
+```
+
+```
+./autogen.sh
+./configure \
+	--enable-eap-aka \
+	--enable-eap-aka-3gpp \
+	--enable-eap-aka-3gpp2 \
+	--enable-eap-simaka-reauth \
+	--enable-systemd \
+	--enable-save-keys \
+	--enable-p-cscf \
+	--enable-osmo-epdg
+
+```