compilation problem

Hi,
I am compiling LLVm with clang and I get the following error:

Compiling InitHeaderSearch.cpp for Release+Asserts build
InitHeaderSearch.cpp:29:51: error: clang/Config/config.h :
InitHeaderSearch.cpp: In member function
‘void<unnamed>::InitHeaderSearch::AddDefaultCIncludePaths(const
llvm::Triple&, const clang::HeaderSearchOptions&)’:
InitHeaderSearch.cpp:237: error: ‘C_INCLUDE_DIRS’ was not declared in this scope

I do not know what is wrong.