It seems that make install cannot be modified to be given a single target.
The truth is you don't even need to copy/install the kstars executable anywhere,
You can just run it from wherever it is compiled without any installation.
In Jerry's script, I believe that would be by typing this on the command line:
That what I tend to do.
So it seems to be distribution dependent. I have no issue compiling it on my Pi4 running 64bit openSUSE Tumbleweed.
It has docbook_4 4.5 and docbook-xsl-stylesheets 1.79.2 installed. Maybe that's the difference?