Log debug build status and warn when running benchmarks

Summary:
"34328b4 Use PACKAGE_NAME instead of hardcoding application name in log message (Wladimir J. van der Laan)
0c74e2e Log debug build status and warn when running benchmarks (Wladimir J. van der Laan)

Pull request description:

  Log whether the starting instance of bitcoin core is a debug or release build (--enable-debug).

  Also warn when running the benchmarks with a debug build, to prevent mistakes comparing debug to non-debug results."

This is a backport from Core PR12197: bitcoin/bitcoin#12197

Test Plan:
  cmake .. -DCMAKE_BUILD_TYPE=Debug -GNinja
  ninja check
  ninja bench-bitcoin

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, deadalnix, nakihito, Fabien

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, nakihito, Fabien

Subscribers: Fabien, nakihito

Differential Revision: https://reviews.bitcoinabc.org/D4687

src/bench/bench.cpp

@@ -99,6 +99,10 @@ void benchmark::BenchRunner::RunAll(Printer &printer, uint64_t num_evals,
         std::cerr << "WARNING: Clock precision is worse than microsecond - "
                      "benchmarks may be less accurate!\n";
     }
+#ifdef DEBUG
+    std::cerr << "WARNING: This is a debug build - may result in slower "
+                 "benchmarks.\n";
+#endif
 
     std::regex reFilter(filter);
     std::smatch baseMatch;

src/init.cpp

@@ -1377,7 +1377,13 @@ void InitLogging() {
 
     fLogIPs = gArgs.GetBoolArg("-logips", DEFAULT_LOGIPS);
 
-    LogPrintf("%s version %s\n", CLIENT_NAME, FormatFullVersion());
+    std::string version_string = FormatFullVersion();
+#ifdef DEBUG
+    version_string += " (debug build)";
+#else
+    version_string += " (release build)";
+#endif
+    LogPrintf("%s version %s\n", CLIENT_NAME, version_string);
 }
 
 namespace { // Variables internal to initialization process only