Checkout libaom v3.1.2

ext/aom.cmd

diff --git a/ext/aom.cmd b/ext/aom.cmd
index 59c0d2f..e934d7e 100755
--- a/ext/aom.cmd
+++ b/ext/aom.cmd
@@ -8,7 +8,7 @@
 : # If you're running this on Windows, be sure you've already run this (from your VC2019 install dir):
 : #     "C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Auxiliary\Build\vcvars64.bat"
 
-git clone -b v3.1.1 --depth 1 https://aomedia.googlesource.com/aom
+git clone -b v3.1.2 --depth 1 https://aomedia.googlesource.com/aom
 
 cd aom
 mkdir build.libavif

tests/docker/build.sh

diff --git a/tests/docker/build.sh b/tests/docker/build.sh
index 4591769..aa0d3cc 100644
--- a/tests/docker/build.sh
+++ b/tests/docker/build.sh
@@ -34,7 +34,7 @@
 
 # aom
 cd
-git clone -b v3.1.1 --depth 1 https://aomedia.googlesource.com/aom
+git clone -b v3.1.2 --depth 1 https://aomedia.googlesource.com/aom
 cd aom
 mkdir build.avif
 cd build.avif