Build errors when using the USE_SYSTEM_BOOST cmake option.

[est77]

In CMakeLists.txt, target_link_boost function the correct target names for Boost libraries found by FindBoost()
are Boost::system, Boost::filesystem and Boost::thread.

The current values used ${Boost_XXX_LIBRARY} are not defined and as a result boost includes and libraries are not added to the compiler command line.

[ilelann]

I don't reproduce that.
On a recent Fedora, with dnf install boost-devel done before, I can successfully do :

git clone https://github.com/stlab/adobe_source_libraries.git && mkdir build && cd build && cmake -DUSE_SYSTEM_BOOST=ON ../adobe_source_libraries && make -j && ctest

I miss something ?

[est77]

Maybe it depends on CMake's version? I am using 3.17.3 here.

In recent FindBoost versions, targets are defined as Boost::library_name and the old ${Boost_XXX_LIBRARY} vars seems not be defined.
As a result I have missing include paths and library paths when trying to build.

[ilelann]

cmake version 3.20.5

Note that according to https://cmake.org/cmake/help/latest/module/FindBoost.html Boost_<COMPONENT>_LIBRARY are defined in latest version.
I checked locally with CMake's message, they are definitely pointing to correct .so files.
But they are not "targets".

I tested with Boost::xxx targets. it works for me.
I guess we should switch to the new target version because it covers include paths too.
Current CMakeLists.txt only links .so names, which is enough in most Linux setups since include and lib paths are not really required.

[est77]

Thanks for the PR!

[camio]

Verified that #83 fixes this issue and merged it in.