Allow older CMake version
Created by: masterleinad
At least for CMake 3.10
we need absolute paths for INTERFACE
target_sources
.
Of course, the usual incompatibility(https://stackoverflow.com/questions/42123509/cmake-finds-boost-but-the-imported-targets-not-available-for-boost-version) between Boost
and CMake
still applies, i.e. for CMake 3.10
Boost
version >1.65.1 don't work with imported targets correctly.