SELinux 模块需要使用到 fts 库，所以增加对应的源码文件。

(BSD-3-Clause) depends/fts/fts.h    <- https://github.com/freebsd/freebsd-src/blob/ea31abc261ffc01b6ff5671bffb15cf910a07f4b/include/fts.h
(BSD-3-Clause) depends/fts/fts.c    <- https://github.com/freebsd/freebsd-src/blob/ea31abc261ffc01b6ff5671bffb15cf910a07f4b/lib/libc/gen/fts.cSigned-off-by: NQin Fandong <qinfd@superred.com.cn>

include/fts.h

+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 1989, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)fts.h	8.3 (Berkeley) 8/14/94
+ * $FreeBSD$
+ */
+
+#ifndef	_FTS_H_
+#define	_FTS_H_
+
+#include <sys/_types.h>
+
+typedef struct {
+	struct _ftsent *fts_cur;	/* current node */
+	struct _ftsent *fts_child;	/* linked list of children */
+	struct _ftsent **fts_array;	/* sort array */
+	__dev_t fts_dev;		/* starting device # */
+	char *fts_path;			/* path for this descent */
+	int fts_rfd;			/* fd for root */
+	__size_t fts_pathlen;		/* sizeof(path) */
+	__size_t fts_nitems;		/* elements in the sort array */
+	int (*fts_compar)		/* compare function */
+	    (const struct _ftsent * const *, const struct _ftsent * const *);
+
+#define	FTS_COMFOLLOW	0x001		/* follow command line symlinks */
+#define	FTS_LOGICAL	0x002		/* logical walk */
+#define	FTS_NOCHDIR	0x004		/* don't change directories */
+#define	FTS_NOSTAT	0x008		/* don't get stat info */
+#define	FTS_PHYSICAL	0x010		/* physical walk */
+#define	FTS_SEEDOT	0x020		/* return dot and dot-dot */
+#define	FTS_XDEV	0x040		/* don't cross devices */
+#define	FTS_WHITEOUT	0x080		/* return whiteout information */
+#define	FTS_OPTIONMASK	0x0ff		/* valid user option mask */
+
+#define	FTS_NAMEONLY	0x100		/* (private) child names only */
+#define	FTS_STOP	0x200		/* (private) unrecoverable error */
+	int fts_options;		/* fts_open options, global flags */
+	void *fts_clientptr;		/* thunk for sort function */
+} FTS;
+
+typedef struct _ftsent {
+	struct _ftsent *fts_cycle;	/* cycle node */
+	struct _ftsent *fts_parent;	/* parent directory */
+	struct _ftsent *fts_link;	/* next file in directory */
+	long long fts_number;		/* local numeric value */
+#define	fts_bignum	fts_number	/* XXX non-std, should go away */
+	void *fts_pointer;		/* local address value */
+	char *fts_accpath;		/* access path */
+	char *fts_path;			/* root path */
+	int fts_errno;			/* errno for this node */
+	int fts_symfd;			/* fd for symlink */
+	__size_t fts_pathlen;		/* strlen(fts_path) */
+	__size_t fts_namelen;		/* strlen(fts_name) */
+
+	__ino_t fts_ino;		/* inode */
+	__dev_t fts_dev;		/* device */
+	__nlink_t fts_nlink;		/* link count */
+
+#define	FTS_ROOTPARENTLEVEL	-1
+#define	FTS_ROOTLEVEL		 0
+	long fts_level;			/* depth (-1 to N) */
+
+#define	FTS_D		 1		/* preorder directory */
+#define	FTS_DC		 2		/* directory that causes cycles */
+#define	FTS_DEFAULT	 3		/* none of the above */
+#define	FTS_DNR		 4		/* unreadable directory */
+#define	FTS_DOT		 5		/* dot or dot-dot */
+#define	FTS_DP		 6		/* postorder directory */
+#define	FTS_ERR		 7		/* error; errno is set */
+#define	FTS_F		 8		/* regular file */
+#define	FTS_INIT	 9		/* initialized only */
+#define	FTS_NS		10		/* stat(2) failed */
+#define	FTS_NSOK	11		/* no stat(2) requested */
+#define	FTS_SL		12		/* symbolic link */
+#define	FTS_SLNONE	13		/* symbolic link without target */
+#define	FTS_W		14		/* whiteout object */
+	int fts_info;			/* user status for FTSENT structure */
+
+#define	FTS_DONTCHDIR	 0x01		/* don't chdir .. to the parent */
+#define	FTS_SYMFOLLOW	 0x02		/* followed a symlink to get here */
+#define	FTS_ISW		 0x04		/* this is a whiteout object */
+	unsigned fts_flags;		/* private flags for FTSENT structure */
+
+#define	FTS_AGAIN	 1		/* read node again */
+#define	FTS_FOLLOW	 2		/* follow symbolic link */
+#define	FTS_NOINSTR	 3		/* no instructions */
+#define	FTS_SKIP	 4		/* discard node */
+	int fts_instr;			/* fts_set() instructions */
+
+	struct stat *fts_statp;		/* stat(2) information */
+	char *fts_name;			/* file name */
+	FTS *fts_fts;			/* back pointer to main FTS */
+} FTSENT;
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+FTSENT	*fts_children(FTS *, int);
+int	 fts_close(FTS *);
+void	*fts_get_clientptr(FTS *);
+#define	 fts_get_clientptr(fts)	((fts)->fts_clientptr)
+FTS	*fts_get_stream(FTSENT *);
+#define	 fts_get_stream(ftsent)	((ftsent)->fts_fts)
+FTS	*fts_open(char * const *, int,
+	    int (*)(const FTSENT * const *, const FTSENT * const *));
+FTSENT	*fts_read(FTS *);
+int	 fts_set(FTS *, FTSENT *, int);
+void	 fts_set_clientptr(FTS *, void *);
+__END_DECLS
+
+#endif /* !_FTS_H_ */