Suppress UBSan errors from the AGC

tools/ubsan/blacklist.txt

Index: tools/ubsan/blacklist.txt
diff --git a/tools/ubsan/blacklist.txt b/tools/ubsan/blacklist.txt
index 2510d41ce4eaf66ab5ab4bef83e3d56150dbb1ef..d48b31d2a9ca9dcd0c7ec09257baf299a9cfdfb5 100644
--- a/tools/ubsan/blacklist.txt
+++ b/tools/ubsan/blacklist.txt
@@ -22,6 +22,12 @@ src:*/webrtc/modules/audio_coding/codecs/isac/fix/source/entropy_coding.c
 fun:*FilterBanksTest*CalculateResidualEnergyTester*
 
 #############################################################################
+# The audio processing AGC submodule exhibits a few problems (overflows).
+# https://bugs.chromium.org/p/webrtc/issues/detail?id=5530
+src:*/webrtc/modules/audio_processing/agc/legacy/analog_agc.c
+src:*/webrtc/modules/audio_processing/agc/legacy/digital_agc.c
+
+#############################################################################
 # Ignore errors in common_audio.
 # https://bugs.chromium.org/p/webrtc/issues/detail?id=5486
 src:*/webrtc/common_audio/signal_processing/signal_processing_unittest.cc