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/mmap_exec.c

@@ -0,0 +1,72 @@
+/*
+ * 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) 2013 by Delphix. All rights reserved.
+ */
+
+#include <stdio.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <errno.h>
+
+int
+main(int argc, char *argv[])
+{
+	int error, fd;
+	struct stat statbuf;
+
+	if (argc != 2) {
+		(void) printf("Error: missing binary name.\n");
+		(void) printf("Usage:\n\t%s <binary name>\n",
+		    argv[0]);
+		return (1);
+	}
+
+	errno = 0;
+
+	if ((fd = open(argv[1], O_RDONLY)) < 0) {
+		error = errno;
+		perror("open");
+		return (error);
+	}
+	if (fstat(fd, &statbuf) < 0) {
+		error = errno;
+		perror("fstat");
+		return (error);
+	}
+
+	if (mmap(0, statbuf.st_size,
+	    PROT_EXEC, MAP_SHARED, fd, 0) == MAP_FAILED) {
+		error = errno;
+		perror("mmap");
+		return (error);
+	}
+
+	return (0);
+}