Refactor built-in getty into a standalone getty in /libexec

This patch moves the built-in getty out of Finit into /libexec/finit/,
reducing the size of the Finit binary and simplifying the code.

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

src/util.c

@@ -229,16 +229,6 @@ int fngetint(char *path, int *val)
 	return 0;
 }
 
-/*
- * musl libc default to /dev/null/utmp and /dev/null/wtmp, respectively.
- * See https://www.openwall.com/lists/musl/2012/03/04/4 for reasoning.
- * Also, there's no __MUSL__, so we cannot make a libc-specific #ifdef
- */
-int has_utmp(void)
-{
-	return strncmp(_PATH_UTMP, "/dev/null", 9);
-}
-
 int strtobytes(char *arg)
 {
 	int mod = 0, bytes;