Fix Cycles HIP RT kernel not rebuilding on changes

Changes to the kernel source would not update the HIP RT binaries, leading
to render errors due to the kernel being mismatched with Blender.

The code this was copied from was inside a macro that defines the sources
variable, but it's not defined here.

Ref #109418

Pull Request: https://projects.blender.org/blender/blender/pulls/110073

intern/cycles/kernel/CMakeLists.txt

@@ -666,7 +666,7 @@ if(WITH_CYCLES_DEVICE_HIPRT AND WITH_CYCLES_HIP_BINARIES)
     ${SRC_UTIL_HEADERS})
   set(bitcode_file ${CMAKE_CURRENT_BINARY_DIR}/kernel_rt_gfx.bc)
   set(hiprt_file ${CMAKE_CURRENT_BINARY_DIR}/kernel_rt_gfx.hipfb)
-  set(kernel_sources ${sources})
+  set(kernel_sources ${hiprt_sources})
   set(hiprt_kernel_src "/device/hiprt/kernel.cpp")
   if(WIN32)
     set(hiprt_compile_command ${CMAKE_COMMAND})