Build rustc with incr. ThinLTO so we can benchmark it.

Author: michaelwoerister

src/ci/docker/dist-x86_64-linux/Dockerfile

@@ -102,7 +102,8 @@ ENV RUST_CONFIGURE_ARGS \
       --set target.x86_64-unknown-linux-gnu.ar=/rustroot/bin/llvm-ar \
       --set target.x86_64-unknown-linux-gnu.ranlib=/rustroot/bin/llvm-ranlib \
       --set llvm.thin-lto=true \
-      --set rust.jemalloc
+      --set rust.jemalloc \
+      --set rust.incremental=true
 ENV SCRIPT python2.7 ../x.py dist --host $HOSTS --target $HOSTS
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang