--- rustc-1.12.0/src/librustc_llvm/lib.rs.orig
+++ rustc-1.12.0/src/librustc_llvm/lib.rs
@@ -481,3 +481,6 @@
 mod llvmdeps {
     include! { env!("CFG_LLVM_LINKAGE_FILE") }
 }
+
+#[link(name = "ffi")]
+extern {}