tests: cmd: don't recurse

This confers an >10x speedup on t/z-t/cmd builds (12s -> 1.1s),
gets rid of 23 redundant identical automake specs and gitignores,
and groups the binaries with their common headers

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #13259

tests/zfs-tests/cmd/file/file_common.h

@@ -0,0 +1,70 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#ifndef FILE_COMMON_H
+#define	FILE_COMMON_H
+
+/*
+ * header file for file_* utilities. These utilities
+ * are used by the test cases to perform various file
+ * operations (append writes, for example).
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef _FILE_OFFSET_BITS
+#define	_FILE_OFFSET_BITS 64
+#endif
+
+#ifndef _LARGEFILE64_SOURCE
+#define	_LARGEFILE64_SOURCE
+#endif
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define	BLOCKSZ		8192
+#define	DATA		0xa5
+#define	DATA_RANGE	120
+#define	BIGBUFFERSIZE	0x800000
+#define	BIGFILESIZE	20
+
+extern char *optarg;
+extern int optind, opterr, optopt;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* FILE_COMMON_H */