Add ubsan blacklist for drc_kernel

We enable "flush denormals to zero" so a float-divide-by-zero is
expected.
There is a isbadf check after that division to trim the number to -1 or
1, so it is okay.

BUG=chromium:965725
TEST=$ setup_board --board=amd64-generic --profile=ubsan
     $ ./build_packages --board=amd64-generic adhd
     $ FEATURES=test emerge-amd64-generic adhd

Change-Id: I53a2382a1e218738f0ba4f4d14d8aac4ff50fd4b
Reviewed-on: https://chromium-review.googlesource.com/1666976
Tested-by: Cheng-Yi Chiang <[email protected]>
Commit-Ready: Cheng-Yi Chiang <[email protected]>
Legacy-Commit-Queue: Commit Bot <[email protected]>
Reviewed-by: Dylan Reid <[email protected]>
Reviewed-by: Hsinyu Chao <[email protected]>

Author: chiang831

ubsan_blocklist.txt

@@ -0,0 +1,5 @@
+# Suppress float devide-by-zero error in dsp.
+# https://crbug.com/965725
+[float-divide-by-zero]
+src:cras/src/dsp/drc_kernel.c
+fun:dk_update_envelope