Fix T41783: Cycles baking ignores displacement

Create unique flag for output shaders with displacement data and use it
to calculate transformed normal. Implementation suggested by Brecht Van
Lommel.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D890

intern/cycles/kernel/kernel_bake.h

@@ -253,6 +253,10 @@ ccl_device void kernel_bake_evaluate(KernelGlobals *kg, ccl_global uint4 *input,
 		/* data passes */
 		case SHADER_EVAL_NORMAL:
 		{
+			if ((sd.flag & SD_HAS_BUMP)) {
+				shader_eval_surface(kg, &sd, 0.f, 0, SHADER_CONTEXT_MAIN);
+			}
+
 			/* compression: normal = (2 * color) - 1 */
 			out = sd.N * 0.5f + make_float3(0.5f, 0.5f, 0.5f);
 			break;