I was trying to install KMyMoney from macports on OS X Mavericks. In turn, this attempted a macports install of llvm-gcc42. This produced the error: “The directory that should contain system headers does not exist” macports
The solution is to manually install XCode tools via xcode-select –install
Note that xcode command line tools are supposed to automagically install, but when they do, they don’t create /usr/include, and that’s what’s missing.