Fix environment variable setting

Author: GuillaumeGomez

src/ci/docker/run.sh

@@ -269,7 +269,7 @@ touch $objdir/${SUMMARY_FILE}
 
 extra_env=""
 if [ "$ENABLE_GCC_CODEGEN" = "1" ]; then
-  extra_env="$extra_env --env ENABLE_GCC_CODEGEN=1"
+  extra_env="$EXTRA_ENV --env ENABLE_GCC_CODEGEN=1"
   # If `ENABLE_GCC_CODEGEN` is set and not empty, we add the `--enable-new-symbol-mangling`
   # argument to `RUST_CONFIGURE_ARGS` and set the `GCC_EXEC_PREFIX` environment variable.
   # `cg_gcc` doesn't support the legacy mangling so we need to enforce the new one