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/largest_file.c

@@ -0,0 +1,145 @@
+/*
+ * 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.
+ */
+
+/*
+ * Copyright (c) 2012 by Delphix. All rights reserved.
+ */
+
+#include "file_common.h"
+#include <sys/param.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stdtypes.h>
+#include <unistd.h>
+
+/*
+ * --------------------------------------------------------------
+ *
+ *	Assertion:
+ *		The last byte of the largest file size can be
+ *		accessed without any errors.  Also, the writing
+ *		beyond the last byte of the largest file size
+ *		will produce an errno of EFBIG.
+ *
+ * --------------------------------------------------------------
+ *	If the write() system call below returns a "1",
+ *	then the last byte can be accessed.
+ * --------------------------------------------------------------
+ */
+static void	sigxfsz(int);
+static void	usage(char *);
+
+int
+main(int argc, char **argv)
+{
+	int		fd = 0;
+	offset_t	offset = (MAXOFFSET_T - 1);
+	offset_t	llseek_ret = 0;
+	int		write_ret = 0;
+	int		err = 0;
+	char		mybuf[5] = "aaaa\0";
+	char		*testfile;
+	mode_t		mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
+	struct sigaction sa;
+
+	if (argc != 2) {
+		usage(argv[0]);
+	}
+
+	if (sigemptyset(&sa.sa_mask) == -1)
+		return (errno);
+	sa.sa_flags = 0;
+	sa.sa_handler = sigxfsz;
+	if (sigaction(SIGXFSZ, &sa, NULL) == -1)
+		return (errno);
+
+	testfile = strdup(argv[1]);
+
+	fd = open(testfile, O_CREAT | O_RDWR, mode);
+	if (fd < 0) {
+		err = errno;
+		perror("Failed to create testfile");
+		free(testfile);
+		return (err);
+	}
+
+	llseek_ret = lseek64(fd, offset, SEEK_SET);
+	if (llseek_ret < 0) {
+		err = errno;
+		perror("Failed to seek to end of testfile");
+		goto out;
+	}
+
+	write_ret = write(fd, mybuf, 1);
+	if (write_ret < 0) {
+		err = errno;
+		perror("Failed to write to end of file");
+		goto out;
+	}
+
+	offset = 0;
+	llseek_ret = lseek64(fd, offset, SEEK_CUR);
+	if (llseek_ret < 0) {
+		err = errno;
+		perror("Failed to seek to end of file");
+		goto out;
+	}
+
+	write_ret = write(fd, mybuf, 1);
+	if (write_ret < 0) {
+		if (errno == EFBIG || errno == EINVAL) {
+			(void) printf("write errno=EFBIG|EINVAL: success\n");
+			err = 0;
+		} else {
+			err = errno;
+			perror("Did not receive EFBIG");
+		}
+	} else {
+		(void) printf("write completed successfully, test failed\n");
+		err = 1;
+	}
+
+out:
+	(void) unlink(testfile);
+	free(testfile);
+	close(fd);
+	return (err);
+}
+
+static void
+usage(char *name)
+{
+	(void) printf("%s <testfile>\n", name);
+	exit(1);
+}
+
+static void
+sigxfsz(int signo)
+{
+	(void) signo;
+	(void) printf("\nlargest_file: sigxfsz() caught SIGXFSZ\n");
+}