Config: Disable the use of libvips on 32-bit operating systems

[lastzero]

This seems to be necessary due to compatibility issues between our Go wrapper library and libvips (which is implemented in C).

[Radiokot]

The photoprism:preview-armv7 (f30a713ba3a3868e4b183ca83ee85609eb7674d937a04aa87b0de4ff4234b822) build without PHOTOPRISM_THUMB_LIBRARY option generates correct thumbnails on ARMv7 32-bit computer, which means vips has been successfully disabled automatically.