Small change to allow override SHADOWS_SCREEN define.

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/Shadows.hlsl

 
 #define MAX_SHADOW_CASCADES 4
 
+#ifndef SHADOWS_SCREEN
+#endif
 #endif
 
 SCREENSPACE_TEXTURE(_ScreenSpaceShadowMapTexture);
 {
 #if !defined(_SHADOWS_ENABLED)
     return 1.0h;
-#elif SHADOWS_SCREEN
+#endif
+
+#if SHADOWS_SCREEN
     return SampleScreenSpaceShadowMap(shadowCoord);
 #else
     ShadowSamplingData shadowSamplingData = GetMainLightShadowSamplingData();