thanks everyone for your advices.
i made 2 major mistakes:
in both cases one has to provide additional tools and/or the correct path to them in the Windows system. therefore the "cl.exe not found". MINGW32 has them included.
so, with the sources from github i succeeded to make the app.
the verbosity of the output of the whole proces is quite overwhelming for someone like me. there were a number of warnings: e.g.: "remember to run 'libtool --finish /..../bob~ or: "assignment from incompatible pointer"
is it necessary to do something with them?
@lucas great, you saved me the efforts to find out what to use on XP (MSYS2 doesn't work anymore on XP).
rolf