Add presubmit
diff --git a/.bazelci/presubmit.yml b/.bazelci/presubmit.yml
index 8d7899d..0707da9 100644
--- a/.bazelci/presubmit.yml
+++ b/.bazelci/presubmit.yml
@@ -51,3 +51,13 @@
       - "--ignore_dev_dependency"
     build_targets:
       - "//cc/..."
+  ubuntu_rule_based_toolchains:
+    name: Linux rule-based toolchains
+    platform: ubuntu1804
+    working_directory: examples/rule_based_toolchain
+    build_flags:
+      - "--enable_bzlmod"
+    build_targets:
+      - "//..."
+    test_targets:
+      - "//..."
diff --git a/examples/rule_based_toolchain/toolchain/BUILD b/examples/rule_based_toolchain/toolchain/BUILD
index 927101e..1f3fccc 100644
--- a/examples/rule_based_toolchain/toolchain/BUILD
+++ b/examples/rule_based_toolchain/toolchain/BUILD
@@ -17,6 +17,7 @@
         "@rules_cc//cc/toolchains/actions:cpp_compile_actions",
     ],
     args = [
+        "-Werror",
         "-Wall",
         "-Wextra",
         "-Wpedantic",