[CMake] Can't find boost libs on VS2017 CMake 3.12

[Søren]

Thanks

Debug output shows
* that it already searchs in the right folders.
* It appears to search for the right patterns e.g. 
"boost_chrono-vc141-mt-x64-1_67" (file is there 
"libboost_chrono-vc141-mt-x64-1_67.lib")
* It also states  "Boost_FOUND = 1"

But still that error. So far I can't see from the debug output why it 
fails.