Gentoo's Bugzilla –
Attachment 557146 Details for
Bug 672608dev-lang/rust-1.30.1-r1 with wasm USE flag and sys-devel/llvm-6.0.1 - .../work/rustc-1.30.1-src/src/tools/lld/Common/ErrorHandler.cpp:52:34: error: ‘class llvm::FileOutputBuffer’ has no member named ‘discard’