flush gflags output

last stab at #5999

rts/System/SpringApp.cpp

@@ -167,11 +167,9 @@ static void ConsolePrintInitialize(const std::string& configSource, bool safemod
  */
 SpringApp::SpringApp(int argc, char** argv)
 {
-	// {--,/}help overrides all other flags and causes exit(),
-	// even in the unusual event it is not given as first arg
-	if (argc > 1 && strstr(argv[1], "help") != nullptr)
-		ConsolePrintInitialize("", false);
-
+	// NB
+	//   {--,/}help overrides all other flags and causes exit(),
+	//   even in the unusual event it is not given as first arg
 	gflags::SetUsageMessage("Usage: " + std::string(argv[0]) + " [options] [path_to_script.txt or demo.sdfz]");
 	gflags::SetVersionString(SpringVersion::GetFull());
 	gflags::ParseCommandLineFlags(&argc, &argv, true);

rts/lib/gflags/src/gflags.cc

@@ -135,8 +135,16 @@ using std::sort;
 using std::string;
 using std::vector;
 
+static void flush_exit(int ec) {
+	// exit(1) is not a normal termination, force a flush
+	std::fflush(stdout);
+	std::exit(ec);
+}
+
 // This is used by the unittest to test error-exit code
-void GFLAGS_DLL_DECL (*gflags_exitfunc)(int) = &exit;  // from stdlib.h
+// void GFLAGS_DLL_DECL (*gflags_exitfunc)(int) = &exit;  // from stdlib.h
+//SPRING
+void GFLAGS_DLL_DECL (*gflags_exitfunc)(int) = &flush_exit;
 
 
 // The help message indicating that the commandline flag has been