Guard Avg16x16IntegerOverflow test w/ HIGHBITDEPTH

Guard the EncodeAPI.Avg16x16IntegerOverflow test with
CONFIG_AV1_HIGHBITDEPTH because it requires 12-bit support.

Use ASSERT_EQ on the aom_codec_enc_init() call because the test should
not proceed further if aom_codec_enc_init() fails.

Bug: oss-fuzz:572842743
Change-Id: I6e7dd9393cd46dcc3ef33055524fa29b269e322d

test/encode_api_test.cc

diff --git a/test/encode_api_test.cc b/test/encode_api_test.cc
index eb7497f..d08748a 100644
--- a/test/encode_api_test.cc
+++ b/test/encode_api_test.cc
@@ -4471,6 +4471,7 @@
   ASSERT_EQ(aom_codec_destroy(&enc), AOM_CODEC_OK);
 }
 
+#if CONFIG_AV1_HIGHBITDEPTH
 // A test that reproduces issues.oss-fuzz.com/issues/572842743: signed integer
 // overflow in fill_variance_tree_leaves().
 TEST(EncodeAPI, Avg16x16IntegerOverflow) {
@@ -4597,7 +4598,7 @@
   cfg.rc_min_quantizer = 57;
   cfg.rc_max_quantizer = 63;
   aom_codec_ctx_t enc;
-  EXPECT_EQ(AOM_CODEC_OK,
+  ASSERT_EQ(AOM_CODEC_OK,
             aom_codec_enc_init(&enc, iface, &cfg, AOM_CODEC_USE_HIGHBITDEPTH));
   EXPECT_EQ(AOM_CODEC_OK, aom_codec_control(&enc, AV1E_SET_TILE_ROWS, 5));
   EXPECT_EQ(AOM_CODEC_OK, aom_codec_control(&enc, AV1E_SET_TILE_COLUMNS, 2));
@@ -4690,5 +4691,6 @@
 
   EXPECT_EQ(AOM_CODEC_OK, aom_codec_destroy(&enc));
 }
+#endif  // CONFIG_AV1_HIGHBITDEPTH
 
 }  // namespace