Enable native toolchain and sdk selection including specifying version preferences

It seems quite important to be able to enforce for all source-build choice of native toolchain and sdk. This selection should go down to version of the toolchain and sdk. As an example it should be possible to select compiler toolchain i.e. Intel Windows C++ Compiler and it's version instead of Microsoft MSVC compiler, Windows SDK and it's version against which native binaries are built and to make analogous choices on other OSes and hardware platforms (use Arm toolchain based on Clang for Arm platforms instead of Clang).

IMO this is one of the most important features for top level build platform used for building different public and private "distros".