test: Fix fuzzer compilation on macOS

fixes #19557

Author: freenancial

src/test/fuzz/util.h

@@ -332,7 +332,7 @@ class FuzzedFileProvider
             return 0;
         }
         std::memcpy(buf, random_bytes.data(), random_bytes.size());
-        if (AdditionOverflow((uint64_t)fuzzed_file->m_offset, random_bytes.size())) {
+        if (AdditionOverflow(fuzzed_file->m_offset, (int64_t)random_bytes.size())) {
             return fuzzed_file->m_fuzzed_data_provider.ConsumeBool() ? 0 : -1;
         }
         fuzzed_file->m_offset += random_bytes.size();
@@ -343,7 +343,7 @@ class FuzzedFileProvider
     {
         FuzzedFileProvider* fuzzed_file = (FuzzedFileProvider*)cookie;
         const ssize_t n = fuzzed_file->m_fuzzed_data_provider.ConsumeIntegralInRange<ssize_t>(0, size);
-        if (AdditionOverflow(fuzzed_file->m_offset, n)) {
+        if (AdditionOverflow(fuzzed_file->m_offset, (int64_t)n)) {
             return fuzzed_file->m_fuzzed_data_provider.ConsumeBool() ? 0 : -1;
         }
         fuzzed_file->m_offset += n;