libutil/recurse: Use a single path buffer, and directory fd

This way, we don't use PATH_MAX bytes on the stack per path component,
and don't have to keep copying the complete path around.

rm.c

@@ -1,4 +1,6 @@
 /* See LICENSE file for copyright and license details. */
+#include <fcntl.h>
+
 #include "fs.h"
 #include "util.h"
 
@@ -34,7 +36,7 @@ main(int argc, char *argv[])
 	}
 
 	for (; *argv; argc--, argv++)
-		recurse(*argv, NULL, &r);
+		recurse(AT_FDCWD, *argv, NULL, &r);
 
 	return rm_status || recurse_status;
 }