webrtc contains explicit code to ignore the undefined behavior (RTC_NO_SANITIZE / OverflowingAddS32S32ToS32())

Probably fixes: Integer overflow (unreproducable here)
Probably fixes: 12215/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ILBC_fuzzer-5767142427852800

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>