Add the sytem compiler include paths needed for our static standalone
clang-tidy binary to the list of include paths.
The paths are only added to the compilation units in the generated file
compile_commands.json which is used as input for clang-tidy. Without the
paths clang-tidy can't find the standard C and C++ header files.

The geometries, parameters and input data are not needed when running
clang-tidy, so don't waste time downloading them.
The still downloaded projects include header files which are used by CbmRoot
classes. If these header files are not found by clang-tidy the check of some
compilation units fail.

Use VC in scalar mode, otherwise system and hardware related header files are
needed which couldn't be found.
Fix an issue with an missing header file in KFParticle when using the scalar
VC version.