llvm-config: Let directories aware of CMAKE_CFG_INTDIR.

With llvm-config.exe --bindir --libdir --build-mode, on Visual Studio 2010,

In build tree:
  (OBJ_ROOT)/bin/MinSizeRel
  (OBJ_ROOT)/lib/MinSizeRel
  MinSizeRel

In installed tree:
  (INSTALL_PREFIX)/bin
  (INSTALL_PREFIX)/lib
  MinSizeRel

This is enhancements since r196283.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197467 91177308-0d34-0410-b5e6-96231b3b80d8