if (iar1 == iar2)
Here iar1 and iar2 are decaying to pointers to the first elements of the respective arrays. Since they are two distinct arrays, the pointer values are, of course, different and your comparison tests not equal.
To do an element-wise comparison, you must either write a loop; or use std::array instead
std::array<int, 5> iar1 {1,2,3,4,5};
std::array<int, 5> iar2 {1,2,3,4,5};
if( iar1 == iar2 ) {
// arrays contents are the same
} else {
// not the same
}