Is generating random numbers from hardware performance cryptographically secure?

Suppose I have a program that needs an RNG.

If I were to run arbitrary operations and check the ∆t it takes to do said operations, I could generate random numbers from that

For example:

double start = device.time();
for(int i=0;i<100;i++);//assume compiler doesn't optimize this away
double end = device.time();
double dt = end-start;

dt will be more or less random based on many variables on the device such as battery level, transistor age, room temperature, other processes running, etc.

Now, suppose I keep generating dts and multiply them together as I go, hundreds of times, thousands of times, millions of times, eventually I am left with a very arbitrary number based on values that were more or less randomly calculated by hardware performance benchmarking.

Every time I multiply these dts together, the possible outputs increases exponentially, so determining what possible outputs may be becomes perhaps an impossible task after millions of iterations of this, even if each individual dt value is going to be within a similar range.

---

A thought then occurs, if you have a very consistent device, you may have dt always in the range of say 0.000000011, 0.000000012, 0.000000013, 0.000000014, then the final output number, no matter how many times I iterate and multiply, will be a number of the form 0.000000011^a * 0.000000012^b * 0.000000013^c * 0.000000014^d, that's probably easy to crack.

But then I turn to hashing, suppose rather than multiplying each dt, I concatenate it in string form to the previous values and hash them, so every time I generate a new dt based on hardware performance's random environmental values, I hash. Then at the end I digest the hash to whatever form I need, now the final output number can't be written in a general algebraic form.

Will numbers generated in this form be cryptographically secure?