Gentoo's Bugzilla –
Attachment 380494 Details for
Bug 516790mesa-libs/mesa-10.0.4 - In file included from llvm/invocation.cpp:25: /usr/include/llvm/Support/DataTypes.h:53:3: error: #error "Must #define __STDC_CONSTANT_MACROS before " "#including Support/DataTypes.h"