Shared SPIRV-Tools is not shipped by Debian Bullseye, and is broken if built manually.
Is that a regression? I'm using a build of shared SPIRV-Tools I made myself, and it seems to work fine, although it's an older (v2019.5) version.
We may also want to consider simply getting rid of the SPIRV-Tools dependency. Parsing SPIR-V isn't that complicated, the SPIRV-Tools dependency has always been a bit of a pain, and it would simplify things a bit for Wine's usage of vkd3d.