"Invalid build platform for this proxy" on openSUSE

[Merlin04]

I'm trying to build wine-tkg-git on openSUSE Tumbleweed. The 64-bit build was very easy to get working, but the 32-bit one was missing lots of dependencies at first - I installed all the needed packages and added symlinks to .so files where necessary, but after all that, wine-tkg-git still wouldn't find gstreamer, even though a build following the official Wine instructions (not using the tkg scripts) would work correctly. After some trial and error I figured out that the C compiler not being passed the -m32 flag was somehow breaking this, and so I modified wine-tkg-scripts/build-32.sh to add the flag to the CC variable. Now, the only somewhat-important dependency it complains about when running configure (again, with the m32 flag) is dbus (which is definitely installed, no idea why it can't find it), and the build gets past the dependency checking stage.

Anyway, now when I run non-makepkg-build.sh, I get these errors (only including part of what's printed to the console since it's really long):

dlls/actxprxy/actxprxy_comcat_p.c: In function ‘ICatInformation_RemoteEnumClassesOfCategories_Proxy’:
dlls/actxprxy/actxprxy_comcat_p.c:186:28: error: request for member ‘Simple’ in something not a structure or union
  186 |     return (HRESULT)_RetVal.Simple;
      |                            ^
dlls/actxprxy/actxprxy_comcat_p.c:176:24: warning: variable ‘_RetVal’ set but not used [-Wunused-but-set-variable]
  176 |     CLIENT_CALL_RETURN _RetVal;
      |                        ^~~~~~~
dlls/actxprxy/actxprxy_comcat_p.c: In function ‘ICatInformation_RemoteIsClassOfCategories_Proxy’:
dlls/actxprxy/actxprxy_comcat_p.c:228:28: error: request for member ‘Simple’ in something not a structure or union
  228 |     return (HRESULT)_RetVal.Simple;
      |                            ^
dlls/actxprxy/actxprxy_comcat_p.c:218:24: warning: variable ‘_RetVal’ set but not used [-Wunused-but-set-variable]
  218 |     CLIENT_CALL_RETURN _RetVal;
      |                        ^~~~~~~
dlls/actxprxy/actxprxy_comcat_p.c: At top level:
dlls/actxprxy/actxprxy_comcat_p.c:414:2: error: #error Invalid build platform for this proxy.
  414 | #error Invalid build platform for this proxy.
      |  ^~~~~
dlls/actxprxy/actxprxy_comcat_p.c: In function ‘ICatInformation_RemoteEnumClassesOfCategories_Proxy’:
dlls/actxprxy/actxprxy_comcat_p.c:187:1: warning: control reaches end of non-void function [-Wreturn-type]
  187 | }
      | ^

I'm mostly using the stock customization.cfg, with just these changes:

_staging_version="v9.21"
_wayland_driver="true"

If I manually run configure and make in the source tree generated by non-makepkg-build.sh following Wine's instructions, I don't get this error - the build completes successfully.