Skip UTMP/WTMP update on systems w/o support for it (musl)

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/utmp-api.c

@@ -127,6 +127,9 @@ void utmp_logrotate(void)
 		NULL
 	};
 
+	if (!has_utmp())
+		return 0;
+
 	for (i = 0; files[i]; i++)
 		logrotate(files[i], MAX_NO, MAX_SZ);
 #endif /* LOGROTATE_ENABLED */
@@ -138,6 +141,9 @@ int utmp_set(int type, int pid, char *line, char *id, char *user)
 	struct utmp ut;
 	struct utsname uts;
 
+	if (!has_utmp())
+		return 0;
+
 	switch (type) {
 	case RUN_LVL:
 	case BOOT_TIME:
@@ -188,6 +194,9 @@ static int set_getty(int type, char *tty, char *id, char *user)
 {
 	char *line;
 
+	if (!has_utmp())
+		return 0;
+
 	if (!tty)
 		line = "";
 	else if (!strncmp(tty, "/dev/", 5))