LibC: Implement dummy get_rusage

One port seems to use this function. This dummy just reports no used CPU
time for current process nor children

userspace/libraries/LibC/sys/resource.cpp

@@ -1,7 +1,20 @@
 #include <BAN/Assert.h>
+#include <errno.h>
 #include <sys/resource.h>
 
-int getrusage(int, struct rusage*)
+int getrusage(int who, struct rusage* r_usage)
 {
-	ASSERT_NOT_REACHED();
+	if (who != RUSAGE_CHILDREN && who != RUSAGE_SELF)
+	{
+		errno = EINVAL;
+		return -1;
+	}
+
+	r_usage->ru_stime.tv_sec = 0;
+	r_usage->ru_stime.tv_usec = 0;
+
+	r_usage->ru_utime.tv_sec = 0;
+	r_usage->ru_utime.tv_usec = 0;
+
+	return 0;
 }