[CMake] Introduce LLVM_RUNTIME_OUTPUT_INTDIR and LLVM_LIBRARY_OUTPUT_INTDIR to reduce references to CMAKE_CFG_INTDIR.

Each of them forms like;
  ${CMAKE_BINARY_DIR}/bin/${CMAKE_CFG_INTDIR}
  ${CMAKE_BINARY_DIR}/lib/${CMAKE_CFG_INTDIR}

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197394 91177308-0d34-0410-b5e6-96231b3b80d8
[CMake] ${LLVM_MAIN_SRC_DIR}/include can be represented as ${LLVM_MAIN_INCLUDE_DIR}.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197396 91177308-0d34-0410-b5e6-96231b3b80d8