Install libproxy-dev by entering the following commands in the terminal:
sudo apt update sudo apt install libproxy-dev
Description:
automatic proxy configuration management library (devel)
libproxy is a lightweight library which makes it easy to develop applications proxy-aware with a simple and stable API. . This package contains the development files including vala bindings.
Homepage: https://libproxy.github.io/libproxy/
Version: 0.4.15-1
Section: libdevel