Compatibility mode broken with oss-fuzz

Two recent commits prevent us from upgrading fuzztest as our dependency for our fuzztest tests built on oss-fuzz as they break the check_build `python3 infra/helper.py check_build --sanitizer address libavif`.

The first one is: https://github.com/google/fuzztest/commit/c217c314d458b7eedaaf9a436a0095d396b93820 . The change in https://github.com/google/fuzztest/blob/a990537097b6fd337436f7662fb39fc91fa01f3f/fuzztest/internal/compatibility_mode.cc#L128 gets it to fail and we have to modify it to `if (data.size() == 0) return;`. I am not sure on whether it makes sense though.

The second one is https://github.com/google/fuzztest/commit/0c80b315a00a944b6c2a0284f84f956e577697b8 but it is not because of the bumped dependencies, it is because of `set(GTEST_HAS_ABSL ON)` which forces gtest to use absl flags and apparently has a different parsing. Before that, we could send flags to libfuzzer (deprecated but used on oss-fuzz) the following way: `./test --fuzz=MyTest -- -seed=0 -timeout=10` (here https://github.com/AOMediaCodec/libavif/blob/d074bae4b0b1d7423d102f6d9d5e0c5303971a51/tests/oss-fuzz/build.sh#L123) as officially done upstream at https://github.com/google/oss-fuzz/blob/50c8bb586c0835e6fda39e7e933be197750cdf03/infra/base-images/base-builder/compile_fuzztests.sh#L77