Enable partial code encryption for larger binaries

[Slion]

The encrypted bootloader example demonstrates how to encrypt your binaries and have them securely decrypted in place from SRAM. However, as it is, it only works for the smallest binaries below 448KB minus your stack and heap budget, unless I'm mistaken.

Luckily, as hinted by @kilograham in that forum thread, there could be ways to partially encrypt your binaries. Is there any chance that we could get tools support and an example to do just that?

Ideally, one should be able to encrypt only the application code and not all the SDK and other libraries it is calling. Though my understanding of the linker, ELF and linker scripts is currently far too limited to tell if that would be doable at all.