Advice on getting libstdc++ headers?

First up, just wanted to say this is a really interesting project, I've got some curiosity about using it to do embedded DSL's in C++ through MLIR. If I'm barking up the wrong tree there, feel free to let me know.

But I'm testing this out on a small app

#include<Kokkos_Core.hpp>
int main(int argc, char* argv[]){
  Kokkos::initialize();
  Kokkos::finalize();
}

I can point mlir-clang at the Kokkos_Core header, but that includes and the like, and compilation dies when it sees stdarg and the like. I know that gcc-toolchain isn't supported, so I try a -I /home/projects/x86-64/gcc/11.1/include/c++/11.1.0/. Which bumps me into various versions of

/home/projects/x86-64/gcc/11.1/include/c++/11.1.0/bits/stringfwd.h:70:1: error: unknown type name '_GLIBCXX_BEGIN_NAMESPACE_CXX11'
_GLIBCXX_BEGIN_NAMESPACE_CXX11

Pretty much just "everything about _GLIBCXX doesn't exist." Any thoughts on a path forward here? Should I build libc++ and use that? Am I missing something obvious? Am I trying to do something the project isn't yet trying to support?

In any case, very cool idea, really looking forward to what you're doing here

Start by reproducing the failure with mlir-clang, Kokkos_Core.hpp, and the referenced GCC 11.1 include path. The report provides no named source file, test, or concrete acceptance criterion; resolution would first need to establish whether GCC toolchains or libc++ are supported and document the resulting supported path.