Add system_time bin command which just prints system_time().

This can be used by scripts to do verious performance measurements.
Specifically it can be used to measure the boot time since it represents
the uptime.

build/jam/images/definitions/minimum

@@ -26,7 +26,7 @@ SYSTEM_BIN = [ FFilterByBuildFeatures
 	route
 	safemode screen_blanker screeninfo screenmode setarch setmime settype
 	setversion setvolume shutdown
-	strace su sysinfo
+	strace su sysinfo system_time
 	tcptester telnet telnetd top
 	traceroute trash
 	unchop unmount

src/bin/system_time.cpp

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2015 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		Michael Lotz, [email protected]
+ */
+
+#include <OS.h>
+
+#include <stdio.h>
+
+
+int
+main(int argc, char* argv[])
+{
+	printf("%" B_PRIdBIGTIME "\n", system_time());
+	return 0;
+}