Change check whether TBB was found by cmake-config file
Summary
The find_package(TBB)
with as follows: 1. search for TBBConfig.cmake
and if found use that configuration, otherwise 2. search for tbb.pc
pkg-config file and use that configuration. To decide whether the first step was successfull, I have to check whether the TBB package was found and that the corresponding TBB::tbb
target is available in the package. Otherwise this package would not be usable for us.