Consider re-using our LLVM/Clang to build Rust
Rust re-builds LLVM, which takes a long time.
We could simply reuse the LLVM/Clang we build, and reduce the Rust compiling time, by adding
-DLLVM_INSTALL_UTILS=ON to the options we use to compile Clang.
The only disadvantage is that we link everything to the updated libstdc++.
On Rust we currently pass
--enable-llvm-static-stdcpp. In my test I've removed it and defined
-DLLVM_STATIC_LINK_CXX_STDLIB=ON on Clang, but it wasn't enough.
As a workaround, we could either create a project that extracts libstdc++ from GCC, and provides it to projects that want to use Rust without a dependency on GCC (currently only cbindgen), or copy libstdc++ also to Rust.