Undesirable inclusion of `<iostream>` for freestanding compilers

[simvv-exe]

It is an undesirable to include <iostream> for freestanding compilers. This is especially true for embedded devices that do not have a cout. As you can see in this example https://godbolt.org/z/8vrdv8 call to std::ios_base::Init::Init() cannot be optimized even if you dont use cout and even at maximum optimization level. But this is still add overhead by increasing compilation time, producing larger binaries and increasing startup time.

[CelticMinstrel]

Note: I think you only need <ostream> and not <iostream>. You might even be able to get away with just <iosfwd>.