What causes this build log message: "Shader import version has changed; will reimport all shaders..."

Log message: “Shader import version has changed; will reimport all shaders…”

This log message is appearing in my build log, and shaders are being recompiled, even when nothing (that I know of) has changed between builds. What can cause this message to occur?

Unity version 2020.1.17f1

Experiencing the same annoying issue with Unity 2019.4.30

Getting the same issue in Unity 2020.3.16f1 LTS and wondering what the cause of this could be.