HELP: configure: error:

I am trying to compiler the clang followed the
http://clang.llvm.org/get_started.html ,and facing this problem when on the
6th steps,I was wondering if everybody could help me ?I don't know what to
do with it .
configure: error: Selected compiler could not find or parse C++ standard
library headers. Rerun with CC=c-compiler CXX=c++-compiler ./configure ...

What compiler is currently set to CC/CXX? Do you have a build of clang on your path? If so, which version of clang?