softpipe: Add a dummy field to sp_fragment_shader_variant_key
Fixes a build break from !13731 (merged), and adds softpipe files as triggers for Windows MSVC build to prevent it from breaking again.
/cc @anholt
Fixes a build break from !13731 (merged), and adds softpipe files as triggers for Windows MSVC build to prevent it from breaking again.
/cc @anholt