Cxx17 refac ci trivial (#4507)

* guard gmtime_r with HAVE_GMTIME_R properly

* resolve dash-cppcheck linter error

* Mark stuff as override to resolve compiler warnings

Co-authored-by: Wladimir J. van der Laan <laanwj@protonmail.com>

src/coinjoin/server.cpp

@@ -538,12 +538,12 @@ bool CCoinJoinServer::IsInputScriptSigValid(const CTxIn& txin) const
     txNew.vin.clear();
     txNew.vout.clear();
 
-    int i = 0;
     int nTxInIndex = -1;
     CScript sigPubKey = CScript();
 
     {
         LOCK(cs_coinjoin);
+        int i = 0;
         for (const auto &entry: vecEntries) {
             for (const auto &txout: entry.vecTxOut) {
                 txNew.vout.push_back(txout);

src/dbwrapper.h

@@ -577,7 +577,7 @@ protected:
     struct ValueHolderImpl : ValueHolder {
         ValueHolderImpl(const V &_value, size_t _memoryUsage) : ValueHolder(_memoryUsage), value(_value) {}
 
-        virtual void Write(const CDataStream& ssKey, CommitTarget &commitTarget) {
+        virtual void Write(const CDataStream& ssKey, CommitTarget &commitTarget) override {
             // we're moving the value instead of copying it. This means that Write() can only be called once per
             // ValueHolderImpl instance. Commit() clears the write maps, so this ok.
             commitTarget.Write(ssKey, std::move(value));

src/interfaces/node.cpp

@@ -79,15 +79,15 @@ public:
 class MasternodeSyncImpl : public Masternode::Sync
 {
 public:
-    bool isSynced()
+    bool isSynced() override
     {
         return masternodeSync.IsSynced();
     }
-    bool isBlockchainSynced()
+    bool isBlockchainSynced() override
     {
         return masternodeSync.IsBlockchainSynced();
     }
-    std::string getSyncStatus()
+    std::string getSyncStatus() override
     {
         return masternodeSync.GetSyncStatus();
     }

src/qt/masternodelist.cpp

@@ -36,7 +36,7 @@ public:
         QTableWidgetItem(text, type),
         itemData(data) {}
 
-    bool operator<(const QTableWidgetItem& other) const
+    bool operator<(const QTableWidgetItem& other) const override
     {
         return itemData < ((CMasternodeListWidgetItem*)&other)->itemData;
     }

src/wallet/wallet.cpp

@@ -5284,10 +5284,10 @@ bool CWallet::AutoBackupWallet(const fs::path& wallet_path, std::string& strBack
     // Create backup of the ...
     struct tm ts;
     time_t time_val = GetTime();
-#ifdef _MSC_VER
-    gmtime_s(&ts, &time_val);
-#else
+#ifdef HAVE_GMTIME_R
     gmtime_r(&time_val, &ts);
+#else
+    gmtime_s(&ts, &time_val);
 #endif
     std::string dateTimeStr = strprintf(".%04i-%02i-%02i-%02i-%02i",
             ts.tm_year + 1900, ts.tm_mon + 1, ts.tm_mday, ts.tm_hour, ts.tm_min);