To see all possble windres parameters, you can request help:
x86_64-w64-mingw32-windres.exe --help
For Windows 32 bit format you need coff format with pe-i386 target.
Basically, you have to add -F pe-i386 (or --target=pe-i386) after -O coff flag to your command line if you generate it manually.
In GNU autotools it's about the RCFLAGS. So if there's some configure script, just add
./configure RCFLAGS="--output-format=coff --target=pe-i386" ........