no probs, the thing is that I made a mistake myself . When we use a cubemap we output radial distance from the light not depth (which we could if we decide to not to go for cubemaps but for 6 spot lights to approximate the environment surrounding the point light).
So, my question was wrong in the first place.
Since I decided to use cubemaps for spot light then I MUST use render target in order to write color along with depthstencil to have depth test.
So sorry for my question