Windows XP Pro x64 was released on April 25, 2005 and consumer
processors supporting x86-64 have been around almost as long. Although
there are still 32-bit Windows images available there is not much of a
point maintaining support for these. We also never did any x86 builds
for non-Windows platforms in CI so we don't even know if we work on
those. You might still be able to build 32-bit binaries via CMake.