fix for latest rustc

Author: RalfJung

.travis.yml

@@ -10,7 +10,7 @@ matrix:
       rust: nightly
       if: branch = staging OR branch = trying OR type = pull_request
     - env: TARGET=x86_64-unknown-linux-gnu
-      rust: nightly-2018-12-01
+      rust: nightly-2018-12-01 # old version without rustc-std-workspace-core
       if: branch = staging OR branch = trying
 
     # Linux (build only)

src/sysroot.rs

@@ -401,6 +401,7 @@ impl Blueprint {
 
         Blueprint::add_patch(&mut patch, src.path().join("tools"), "rustc-std-workspace-core")?;
         Blueprint::add_patch(&mut patch, src.path().join("tools"), "rustc-std-workspace-alloc")?;
+        Blueprint::add_patch(&mut patch, src.path().join("tools"), "rustc-std-workspace-std")?;
 
         // Compose dependency sections
         let deps = match (