Blender Git Loki

Fix cmake not triggering rebuild on .glsl changes

At least on windows we do not re-run datatoc when the .glsl files change.

To test is simple, just change edit_mesh_overlay_common_lib.glsl
remove lines, write plain text, ..., now rebuild and go in edit mode
with the default cube.

I also had to remove the entry in gpu/CMakeLists.txt for
gpu_shader_material.glsl since this was being tracked directly, as well
as running data_to_c_simple (otherwise CMake raises an error for
duplicated entries).

We probably want to do the same for the other datatoc functions.

Reviewers: LazyDodo, brecht
Differential Revision: https://developer.blender.org/D3803