make warnings 0.18.0rc1 #15539

unsure if worth reporting or not but I get these warnings on Debian

  CXX      leveldb/util/leveldb_libleveldb_a-logging.o
leveldb/util/logging.cc: In function ‘bool leveldb::ConsumeDecimalNumber(leveldb::Slice*, uint64_t*)’:
leveldb/util/logging.cc:58:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
           (v == kMaxUint64/10 && delta > kMaxUint64%10)) {
                                  ~~~~~~^~~~~~~~~~~~~~~
  CXX      leveldb/util/leveldb_libleveldb_a-options.o
  CXX      leveldb/util/leveldb_libleveldb_a-status.o
  CXX      leveldb/port/leveldb_libleveldb_a-port_posix.o
leveldb/port/port_posix.cc: In function ‘bool leveldb::port::HasAcceleratedCRC32C()’:
leveldb/port/port_posix.cc:60:15: warning: ‘ecx’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   return (ecx & (1 << 20)) != 0;
          ~~~~~^~~~~~~~~~~~

  CXX      bench/bench_bench_bitcoin-base58.o
bench/base58.cpp: In function ‘void Base58Decode(benchmark::State&)’:
bench/base58.cpp:52:39: warning: ignoring return value of ‘bool DecodeBase58(const char*, std::vector<unsigned char>&)’, declared with attribute warn_unused_result [-Wunused-result]
         (void) DecodeBase58(addr, vch);
                                       ^

yes me too

 warning: comparison between signed and unsigned integer expressions [-Wsign-compar
]
           (v == kMaxUint64/10 && delta > kMaxUint64%10)) {
                                  ~~~~~~^~~~~~~~~~~~~~~
  CXX      leveldb/util/leveldb_libleveldb_a-options.o
  CXX      leveldb/util/leveldb_libleveldb_a-status.o
  CXX      leveldb/port/leveldb_libleveldb_a-port_posix.o
leveldb/port/port_posix.cc: In function ‘bool leveldb::port::HasAcceleratedCRC32C()’:
leveldb/port/port_posix.cc:60:15: warning: ‘ecx’ may be used uninitialized in this function [-Wmaybe-uninitialize
]
   return (ecx & (1 << 20)) != 0;
          ~~~~~^~~~~~~~~~~~