This is an attempt at keeping a log of what needs to be done to build KStars from source on Windows using the emerge tool.
This article: https://techbase.kde.org/Getting_Started/Build/Windows/emerge is great for almost all things.
If you are using Windows 10, please see the notes at the very bottom of the page
Also, do not try to use Cygwin to get python and git. The entire process does not want you to have the standard GNU tools in path etc. Instead, get them from the standard installers at python.org and git-scm.com
When installing git using the installer from git-scm.com, make sure you choose the option where git is accessible from command line, but the MinGW tools are not added to the path (Second option out of the three as of this writing). Adding the MinGW32 tools to the path ends up causing trouble while building with the MinGW compiler.
Please note that emerge has a verbose mode (emerge --verbose) which is very helpful for diagnosing any problems.
Building Qt packages
First build Qt Base by emerging it
For some strange reason, emerge may get stuck half way in powershell. It looks like hitting enter periodically ensures that the process goes on (why????). Of course this could just be coincidence but it seems unlikely.