[include-cleaner] Fix building with LLVM_LINK_LLVM_DYLIB=ON on mingw

Make sure to use clang_target_link_libraries, which skips linking
against libraries and links against libclang-cpp instead, if
LLVM_LINK_LLVM_DYLIB is enabled.

This fixes errors like these:

ld.lld: error: duplicate symbol: clang::PPCallbacks::~PPCallbacks()
>>> defined at libclangLex.a(PPCallbacks.cpp.obj)
>>> defined at libclang-cpp.dll