glsl: add new gl_nir_link_glsl() helper

This will allow us to do some linking in NIR that was previously
done by the GLSL IR linker. To start with this just has calls for
linking atomics.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>

src/compiler/glsl/gl_nir_linker.h

@@ -39,6 +39,8 @@ bool gl_nir_link_spirv(struct gl_context *ctx,
                        struct gl_shader_program *prog,
                        const struct gl_nir_linker_options *options);
 
+bool gl_nir_link_glsl(struct gl_context *ctx, struct gl_shader_program *prog);
+
 bool gl_nir_link_uniforms(struct gl_context *ctx,
                           struct gl_shader_program *prog,
                           bool fill_parameters);