Add -Wundef to the CI scripts when building with Bazel

The CMake build already adds -Wundef for gcc/clang. This change makes sure that
the gcc/clang Bazel builds also compile correctly with -Wundef (#3267).

PiperOrigin-RevId: 514864451
Change-Id: I7798a4a4c68d037e23625db24ee29df454367734

ci/linux-presubmit.sh

@@ -78,6 +78,7 @@ time docker run \
       --copt="-Wall" \
       --copt="-Werror" \
       --copt="-Wuninitialized" \
+      --copt="-Wundef" \
       --copt="-Wno-error=pragmas" \
       --distdir="/bazel-distdir" \
       --features=external_include_paths \
@@ -99,6 +100,7 @@ for std in ${STD}; do
         --copt="-Wall" \
         --copt="-Werror" \
         --copt="-Wuninitialized" \
+        --copt="-Wundef" \
         --define="absl=${absl}" \
         --distdir="/bazel-distdir" \
         --features=external_include_paths \
@@ -123,6 +125,7 @@ for std in ${STD}; do
         --copt="-Wall" \
         --copt="-Werror" \
         --copt="-Wuninitialized" \
+        --copt="-Wundef" \
         --define="absl=${absl}" \
         --distdir="/bazel-distdir" \
         --features=external_include_paths \

ci/macos-presubmit.sh

@@ -66,6 +66,7 @@ for absl in 0 1; do
   ${BAZEL_BIN} test ... \
     --copt="-Wall" \
     --copt="-Werror" \
+    --copt="-Wundef" \
     --cxxopt="-std=c++14" \
     --define="absl=${absl}" \
     --features=external_include_paths \