I’m not an expert but I’ve been down part of this path and kept notes.

You have to use architecture=x86/address-model=%z/stagedir=stage%z

Where %z is 32 or 64.

Then copy the staged libraries into library folders with names differing by Win32 versus x64; then you can use the Visual Studio build-in macro $(PlatformName) in your project files or Tools/Options library path settings to select the right folder.

You’re on your own to extend this to two versions of Studio.

If you don’t specify the architecture and address model I’ve seen problems with intermediate folders being shared between 32- and 64-bit builds, breaking one or both.  You may want to call for a full rebuild anyway to get around the issue.

My notes call for specifying –a –d0, release or debug, and stage as well.  Good luck.  Release and Debug use different filenames, as do the various combinations of link and runtime-link options, so you can do all of those builds into the same stage folder.