enable_ray_tracing_shader_debug_symbols pragma doesn't include shader source into debug symbols

When using #pragma enable_ray_tracing_shader_debug_symbols in HLSL code, the pragma doesn't cause the shader source to be included into debug symbols.

How to reproduce (have a ray tracing ready GPU):

1. Clone and open the project from https://github.com/INedelcu/PathTracingDemo
2. Open RayGenerator.raytrace from Assets/Shaders and add #pragma enable_ray_tracing_shader_debug_symbols to the HLSL source.
3. Build any of the scenes.
4. Open the built player in PIX or NVIDIA NSIGHT.
5. Notice that HLSL source code is not included and cannot be debugged.