Migration from wxWidgets 3.1.3 to wxWidgets 2.8.12 - wx-config isn't generated

Question

I am using centOS 8 and trying to install pgAgent in version 3.4.0 on my server.

What I have done so far:

1. Successfully installed cmake, cpack, ctest, wxWidgets-3.1.3, wxGTK-2.8.12.
2. Uninstalled wxWidgets-3.1.3 by using 'make uninstall' after applying 'make install'.
3. Deleted wx-config, wxrc, wxrc-3.1 from /usr/local/bin/.
4. Installed wxWidgets-2.8.12 by using 'make install', and 'sudo ldconfig' has been applied.

Current status:

1. pgAgent cannot be installed and returns "No wxWidgets installation could be found."

2. wxWidgets-2.8.12 cannot be installed with cmake as it is "not in CMakeLists.txt".

3. "wx-config --version" is not found and the file wx-config is not created when wxWidgets-2.8.12 is installed. (This is also true before the deletion of wx-config, as the old config for version 3.1.3 remains and no 2.9 config file appears during installation.

Desired result: Get pgAgent installed.

PS. Some website suggests me to "completely uninstall" the old wxWidgets and then install the new one, which I don't understand how to achieve that. (The official website said I should uninstall it in the way I install it, which does not modify wx-config.)