Enable support for higher bitdepth on aom library

Without this writing a 16bit heif/avif image leads to segmentation
faults.

See,
* akash-akya/vix#109
* lovell/sharp#3358

build/lin.sh

@@ -255,7 +255,7 @@ AOM_AS_FLAGS="${FLAGS}" cmake -G"Unix Makefiles" \
   -DCMAKE_TOOLCHAIN_FILE=${ROOT}/Toolchain.cmake -DCMAKE_INSTALL_PREFIX=${TARGET} -DCMAKE_INSTALL_LIBDIR=lib -DCMAKE_BUILD_TYPE=MinSizeRel \
   -DBUILD_SHARED_LIBS=FALSE -DENABLE_DOCS=0 -DENABLE_TESTS=0 -DENABLE_TESTDATA=0 -DENABLE_TOOLS=0 -DENABLE_EXAMPLES=0 \
   -DCONFIG_PIC=1 -DENABLE_NASM=1 ${WITHOUT_NEON:+-DENABLE_NEON=0} ${DARWIN_ARM:+-DCONFIG_RUNTIME_CPU_DETECT=0} \
-  -DCONFIG_AV1_HIGHBITDEPTH=0 -DCONFIG_WEBM_IO=0 \
+  -DCONFIG_AV1_HIGHBITDEPTH=1 -DCONFIG_WEBM_IO=0 \
   ..
 make install/strip