Resolving "_clock$UNIX2003", referenced from" error

I was trying to build Unity 3D project for simulator SDK. I wanted to get different screen size screen shot. But when I tried to build it I got following build error.

_clock$UNIX2003", referenced from

I found one work around to resolve this issue. We need to add following patch to main.mm file.

#include <time.h>

// "_clock$UNIX2003", referenced from:
//Temporary hack for building Simulator Project for Unity
extern "C"
{
    clock_t
    clock$UNIX2003(void)
    {
        return clock();
    }
}

Once I added above patch build started working fine for me and I was able to run project on Simulator.