sectionsd: move function build_time() to helpers

Origin commit data
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Commit: 3c23415516
Author: vanhofen <vanhofen@gmx.de>
Date: 2022-01-11 (Tue, 11 Jan 2022)

Origin message was:
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- sectionsd: move function build_time() to helpers

src/system/helpers.cpp

@@ -2032,6 +2032,15 @@ bool isDigitWord(std::string str)
 	return true;
 }
 
+time_t GetBuildTime()
+{
+	static const char *built = __DATE__ " " __TIME__;
+	struct tm t;
+	t.tm_isdst = -1;
+	strptime(built, "%b %d %Y %H:%M:%S", &t);
+	return mktime(&t);
+}
+
 int getBoxMode()
 {
 	int boxmode = -1;