Cycles OSL kernel fails to compile with OSL-1.12. Adding RenderServices header solves the problem.
FAILED: src/kernel/osl/CMakeFiles/cycles_kernel_osl.dir/osl_services.cpp.o
error: invalid use of incomplete type ‘class OSL_v1_12::RendererServices’
78 | class OSLRenderServices : public OSL::RendererServices {
| ^~~~~~~~~~~~~~~~