half_ and native_ functions not compiling in Samsung Galaxy S7

I am trying to optimize my OpenCL code running on a Samsung Galaxy S7 (SM-G930F) with an Exynos Octa 8890 and a Mali-T880 using Android. According to OpenCL-Z the gpu supports OpenCL 1.2 full profile. I have a lot of OpenCL code correctly compiling and running. However, I cannot use any of the half_* or native_* functions such as: half_sin or native_sin. As soon as I add one of them I get a CL_BUILD_FAILURE when compiling the kernel. This is one kernel where such behaviour happens:

#pragma OPENCL EXTENSION cl_khr_fp16 : enable
half distancePointToEllipse(short2 point, half2 ecenter, half phi, half a, half b)
{
	half2 t = convert_half2(point) - ecenter;
	half angle = atan2(t.y, t.x) - phi;
	half cos1, sin1;
	//cos1 = native_cos(angle);
	//sin1 = native_sin(angle);
	sin1 = sincos(angle, &cos1);
	half tx = a * a * cos1 * cos1;
	half ty = b * b * sin1 * sin1;
	//half c = native_sqrt(tx + ty);
	//half d = native_sqrt(t.x * t.x + t.y * t.y);
	half c = sqrt(tx + ty);
	half d = hypot(t.x, t.y);
	return fabs(d - c);
}

And this is the code used to compile it:

	auto program_RANSACEllipses = cl::Program(context, CL_RANSAC_ELLIPSES_KERNEL, true);
	program_RANSACEllipses.build("-cl-std=CL1.2");
	Kernels::RANSACEllipses = cl::Kernel(program_RANSACEllipses, "RANSAC");

I have downloaded the headers for OpenCL 1.2 from khronos.

Do you know what am I doing wrong?