Revert r200150, "[CMake] tablegen(): Use -I <dir> according to the list by include_directories()."

It missed include/llvm/Target. Could I avoid GLOB_RECURSE anyways? :(
FYI, I intended to prune ${LLVM_MAIN_INCLUDE_DIR} in TableGen.cmake in r200150.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200730 91177308-0d34-0410-b5e6-96231b3b80d8