Fix fuzz tests to work on oss-fuzz

- the tests now build/run/check_build with libfuzzer on oss-fuzz
- centipede is removed as it builds/runs but do not check_build
(timeout due to arguments not parsed correctly)

Bug: oss-fuzz:69508

Change-Id: Id063565fc4cce02fc5e36c7d8499d6de9ff54345

tests/fuzzer/oss-fuzz/build.sh

@@ -39,21 +39,27 @@
 set -eu
 
 # Avoid fuzz engines that do not compile.
-if [[ "$FUZZING_ENGINE" != "libfuzzer" && "$FUZZING_ENGINE" != "centipede" ]]; then
+if [[ "$FUZZING_ENGINE" != "libfuzzer" ]]; then
   exit
 fi
 
+EXTRA_CMAKE_FLAGS=""
+if [ "$FUZZING_ENGINE" == "libfuzzer" ]
+then
+  export CXXFLAGS="${CXXFLAGS} -DFUZZTEST_COMPATIBILITY_MODE"
+  EXTRA_CMAKE_FLAGS="-DFUZZTEST_COMPATIBILITY_MODE=libfuzzer"
+fi
+
 # limit allocation size to reduce spurious OOMs
 WEBP_CFLAGS="$CFLAGS -DWEBP_MAX_IMAGE_SIZE=838860800" # 800MiB
 
 export CFLAGS="$WEBP_CFLAGS"
-cmake -S . -B build -DWEBP_BUILD_FUZZTEST=ON
+cmake -S . -B build -DWEBP_BUILD_FUZZTEST=ON ${EXTRA_CMAKE_FLAGS}
 cd build && make -j$(nproc) && cd ..
 
 find $SRC/libwebp-test-data -type f -size -32k -iname "*.webp" \
   -exec zip -qju fuzz_seed_corpus.zip "{}" \;
 
-# build fuzztests
 # The following is taken from https://github.com/google/oss-fuzz/blob/31ac7244748ea7390015455fb034b1f4eda039d9/infra/base-images/base-builder/compile_fuzztests.sh#L59
 # Iterate the fuzz binaries and list each fuzz entrypoint in the binary. For
 # each entrypoint create a wrapper script that calls into the binaries the