For mingw32:
- We use the binaries provided by MSYS2, which do not go back as far as
libc++ 8. We use libc++ 9 here, matching the LLVM version we will be
switching to in a subsequent commit (to match the LLVM version used by
Rust 1.44). We manually specify the path to the libc++ headers,
because they don't match the headers used by Clang itself.
- We now require at least mingw-w64 6.0.0, which fixes two Clang
compilation bugs:
- 1bd66b53be
- 82b169c573
Darwin is ignored, as the Xcode SDK includes libc++.
For all other targets, we use the static libraries included in Clang
releases. We reuse the files we downloaded in native_clang for native
compilation, instead of fetching the archive twice.