gl_shader_cache: Add missing new-line on emitted GLSL

Add missing new-line. This caused shaders using local memory and shared
memory to inject a preprocessor GLSL line after an expression (resulting
in invalid code).

It looked like this:
shared uint smem[8];#define LOCAL_MEMORY_SIZE 16

It should look like this (addressed by this commit):
shared uint smem[8];
\#define LOCAL_MEMORY_SIZE 16