helpers: add function to get backup suffix

Origin commit data
------------------
Commit: 427a949807
Author: vanhofen <vanhofen@gmx.de>
Date: 2020-11-12 (Thu, 12 Nov 2020)

Origin message was:
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- helpers: add function to get backup suffix

src/system/helpers.cpp

@@ -54,6 +54,7 @@
 //#include <driver/framebuffer.h>
 #include <system/helpers.h>
 #include <system/helpers-json.h>
+#include <lib/libnet/libnet.h>
 #include <gui/update_ext.h>
 #include <libmd5sum.h>
 #define MD5_DIGEST_LENGTH 16
@@ -623,6 +624,13 @@ std::string getFileExt(std::string &file)
 	return _getBaseName(f, ".");
 }
 
+std::string getBackupSuffix()
+{
+	std::string hostName = "";
+	netGetHostname(hostName);
+
+	return hostName + getNowTimeStr("_%Y%m%d_%H%M");
+}
 
 std::string getNowTimeStr(const char* format)
 {