message: build: fix ubsan oss-fuzz build.
  We were still failing ClusterFuzz builds for ubsan, another external_cmake regression.
  Risk level: Low
  Testing: oss-fuzz undefined Docker build.
diff: @@ -39,7 +39,8 @@ def main():
  #
  # Similar behavior exists for Clang's `-stdlib=libc++` flag, so we handle
  # it in the same test.
  - if "-static-libstdc++" in sys.argv[1:] or "-stdlib=libc++" in sys.argv[1:]:
  + if ("-static-libstdc++" in sys.argv[1:] or "-stdlib=libc++" in sys.argv[1:] or
  + "-std=c++0x" in sys.argv[1:]):
  compiler = envoy_real_cxx
  else:
  compiler = envoy_real_cc
  @@ -62,7 +63,7 @@ def main():
  # unless the user has explicitly set environment variables
  # before starting Bazel. But here in $PWD is the Bazel sandbox,
  # which will be deleted automatically after the compiler exits.
  - (flagfile_fd, flagfile_path) = tempfile.mkstemp(dir='./', suffix=".linker-params")
  + (flagfile_fd, flagfile_path) = tempfile.mkstemp(dir="./", suffix=".linker-params")
  with closing_fd(flagfile_fd):
  sanitize_flagfile(arg[len("-Wl,@"):], flagfile_fd)
  argv.append("-Wl,@" + flagfile_path)
  