Files are a copy of https://github.com/msys2/MINGW-packages-dev/tree/master/mingw-w64-qt4 (using that procedure)
I reproduce here this legacy mingw-w64 package which is still currently used in TeXmacs for windows but no longer available readily built in the msys2 repo. Unfortunately, building the package anew also fails with the current msys2...
In the release, I provide the last i686 binary (32bit) that was in the repo and that is needed for building TeXmacs.
2021-01-18: updated to build on Win10. Many new patches (several security patches) picked from Mageia Cauldron qt4-4.8.7-35.mga8.src.rpm