[envoy] fix ubsan build (google#2664)

Signed-off-by: Lizan Zhou <[email protected]>

projects/envoy/build.sh

@@ -15,9 +15,8 @@
 #
 ################################################################################
 
-# Disable UBSan vptr since target built with -fno-rtti.
-export CFLAGS="$CFLAGS -fno-sanitize=vptr"
-export CXXFLAGS="$CXXFLAGS -fno-sanitize=vptr"
+export CFLAGS="$CFLAGS"
+export CXXFLAGS="$CXXFLAGS"
 
 declare -r FUZZER_TARGETS_CC=$(find . -name *_fuzz_test.cc)
 declare -r FUZZER_TARGETS="$(for t in ${FUZZER_TARGETS_CC}; do echo "${t:2:-3}"; done)"
@@ -39,6 +38,13 @@ done
 for f in ${CXXFLAGS}; do
   echo "--cxxopt=${f}" "--linkopt=${f}"
 done
+
+if [ "$SANITIZER" = "undefined" ]
+then
+  # Bazel uses clang to link binary, which does not link clang_rt ubsan library for C++ automatically.
+  # See issue: https://github.com/bazelbuild/bazel/issues/8777
+  echo "--linkopt=\"$(find $(llvm-config --libdir) -name libclang_rt.ubsan_standalone_cxx-x86_64.a | head -1)\""
+fi
 )"
 
 declare BAZEL_BUILD_TARGETS=""