bx::normalize return bad result when simd is enable on macOS(M1)/iOS platform about bx

[cloudwu]

https://github.com/bkaradzic/bx/blob/master/include/bx/inline/math.inl#L665

I think use rsqrt would be better

  const float invLen = rsqrt(dot(_a, _a));

Because sqrt is implemented with rsqrt https://github.com/bkaradzic/bx/blob/master/include/bx/inline/simd_ni.inl#L200-L211

On this issue, I suggest to clamp (_dir.y ,-1, 1) in toLatLong

inline void toLatLong(float* _outU, float* _outV, const Vec3 _dir)
{
	const float phi   = atan2(_dir.x, _dir.z);
	const float theta = acos(clamp(_dir.y, -1, 1));

	*_outU = (kPi + phi)/kPi2;
	*_outV = theta*kInvPi;
}

[bkaradzic]

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