CI: use rust.debug-assertions = false for x86_64-gnu-tools

Author: jieyouxu

src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile

@@ -79,6 +79,10 @@ ENV PATH="/node/bin:${PATH}"
 COPY host-x86_64/x86_64-gnu-tools/browser-ui-test.version /tmp/
 
 ENV RUST_CONFIGURE_ARGS \
+  # NOTE(jieyouxu): currently rustc alt builds do *not* have rustc debug
+  # assertions enabled! Since this job apparently needs to force CI rustc, then
+  # we cannot set rustc debug assertions to `true`.
+  --set rust.debug-assertions=false \
   --build=x86_64-unknown-linux-gnu \
   --save-toolstates=/tmp/toolstate/toolstates.json \
   --enable-new-symbol-mangling