Add option for Link-Time Optimizations

[toxtran]

Hi!

I noticed that in the CMakeLists.txt file Interprocedural Optimization (IPO, or Link-Lime Optimization (LTO)) is not presented for the project. I suggest to provide an option to enable it on since it will reduce the binary size (always a good thing to have) and will likely improve the application's performance a bit. If you want to read a bit more about LTO, I can recommend starting from from this (GCC) and this (LLVM). CMake can determine LTO support with the check_ipo_support.

In the future, users will be able to choose do they want to use LTO (and get benefits from it) or not.

Thank you!