In Catalina, shader creation will fail because of the following issue:
```
Compilation succeeded with:
program_source:22:21: warning: writable resources in non-void vertex function
vertex VertexOutput vertFunc2(unsigned int vID[[vertex_id]], device Vertex *pos [[buffer(0)]])
^
program_source:22:77: note: writable buffer defined here
vertex VertexOutput vertFunc2(unsigned int vID[[vertex_id]], device Vertex *pos [[buffer(0)]])
^
```
Adding const to ensure the buffer is read-only.
