[CMake] dependencies of cross compiliations

[Torsten Robitzki]

> Am 09.11.2018 um 15:55 schrieb Miller Henry <MillerHenry at JohnDeere.com>:
> 
> There are two options. Each with pros and cons.
> 
> The first what you are doing now, except you use external project https://cmake.org/cmake/help/v3.12/module/ExternalProject.html to build the host tools instead of add_custom_command. It otherwise has all the cons you mention, but are they significant (this is a question that is different for each project)?  Going back to the manual build for host before the target isn’t bad, though it is harder to teach.

I think for the example use case, this will work best. Especially, if there are source files (for example constants) are shared among both platforms.

Thanks,

Torsten