GLSL for OpenGL: appropriate #extension directives not generated for vertex shader that writes to gl_Layer

[ostef]

The following SPIRV vertex shader code produces GLSL code that writes to gl_Layer
without adding the appropriate #extension macros for GL_NV_viewport_array2 or GL_AMD_vertex_shader_layer.

I used the compiler version from commit (104d91a)

color_LUTs.vert.txt