Move check for framebuffer fetch available to main standard shader file since cross compiler appears to be hacked to only enable the macro if its in the main shader file.

Assets/ScriptableRenderPipeline/MobileRenderPipeline/ClassicDeferred/Standard.shader

 
             #include "UnityStandardForwardMobile.cginc"
 
+            #ifdef UNITY_FRAMEBUFFER_FETCH_AVAILABLE
+				half4 fragForward(VertexOutputForwardNew i) : SV_Target3
+			#else
+				half4 fragForward(VertexOutputForwardNew i) : SV_Target
+			#endif 
+			{
+				return singlePassForward(i);
+			}
 
             ENDCG
         }

Assets/ScriptableRenderPipeline/MobileRenderPipeline/ClassicDeferred/StandardSpecular.shader

 
             #include "UnityStandardForwardMobile.cginc"
 
+             #ifdef UNITY_FRAMEBUFFER_FETCH_AVAILABLE
+				half4 fragForward(VertexOutputForwardNew i) : SV_Target3
+			#else
+				half4 fragForward(VertexOutputForwardNew i) : SV_Target
+			#endif 
+			{
+				return singlePassForward(i);
+			}
+
             ENDCG
         }
 

Assets/ScriptableRenderPipeline/MobileRenderPipeline/ClassicDeferred/UnityStandardForwardMobile.cginc

 }
 
 // fragment shader main
-#ifdef UNITY_FRAMEBUFFER_FETCH_AVAILABLE
-	half4 fragForward(VertexOutputForwardNew i) : SV_Target3
-#else
-	half4 fragForward(VertexOutputForwardNew i) : SV_Target
-#endif                                               
+half4 singlePassForward(VertexOutputForwardNew i)                               
 {
 	//float linZ = GetLinearZFromSVPosW(i.pos.w);                 // matching script side where camera space is right handed.
     //float3 vP = GetViewPosFromLinDepth(i.pos.xy, linZ);