possible to add build-win32 with docker?

[aisnote]

thanks.

[kleisauke]

I'm not sure how much work it is to rework build-win32 on top of Docker. You could try using the the MXE-based (makefile-style) build script instead:
https://github.com/libvips/build-win64-mxe

This repository includes support for all four Windows architectures (i686, x86_64, armv7 and arm64). The releases page contains the prebuilt binaries for these architectures.