MONGOCRYPT-834 fuzzing for oss-fuzz

CMakeLists.txt

@@ -588,6 +588,25 @@ if (NOT MONGOCRYPT_CRYPTO STREQUAL none)
    endif ()
 endif ()
 
+option (ENABLE_FUZZING "Build fuzzing targets. Requires a compiler supporting -fsanitize=fuzzer." OFF)
+if (ENABLE_FUZZING)
+   include (CheckCCompilerFlag)
+   set (CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+   check_c_compiler_flag ("-fsanitize=fuzzer-no-link" COMPILER_SUPPORTS_FUZZER)
+   unset (CMAKE_TRY_COMPILE_TARGET_TYPE)
+   if (NOT COMPILER_SUPPORTS_FUZZER)
+      message (FATAL_ERROR
+         "ENABLE_FUZZING is ON but the compiler does not support -fsanitize=fuzzer. "
+      )
+   endif ()
+
+   add_executable (fuzz_mongocrypt EXCLUDE_FROM_ALL test/fuzz_mongocrypt.c)
+   target_include_directories (fuzz_mongocrypt PRIVATE ./src)
+   target_link_libraries (fuzz_mongocrypt PRIVATE mongocrypt_static _mongocrypt::libbson_for_static)
+   target_compile_options (fuzz_mongocrypt PRIVATE -fsanitize=fuzzer)
+   target_link_options (fuzz_mongocrypt PRIVATE -fsanitize=fuzzer)
+endif ()
+
 if (ENABLE_STATIC)
    set (TARGETS_TO_INSTALL mongocrypt mongocrypt_static)
 else ()