libzpool: move zfs_context_os.h from libspl

Keeping the spl/zfs module split, libzpool is the zfs module for
userspace. Headers and functions specific to it belong there.

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861

lib/libzpool/Makefile.am

@@ -1,3 +1,5 @@
+include $(srcdir)/%D%/include/Makefile.am
+
 libzpool_la_CFLAGS  = $(AM_CFLAGS) $(KERNEL_CFLAGS) $(LIBRARY_CFLAGS)
 libzpool_la_CFLAGS += $(ZLIB_CFLAGS)
 

lib/libzpool/include/Makefile.am

@@ -0,0 +1,3 @@
+libzpool_sysdir = $(includedir)/libzpool/sys
+libzpool_sys_HEADERS = \
+	%D%/sys/zfs_context_os.h

lib/libzpool/include/sys/zfs_context_os.h

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: CDDL-1.0
+/*
+ * 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 https://opensource.org/licenses/CDDL-1.0.
+ * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
+ * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ */
+
+#ifndef ZFS_CONTEXT_OS_H_
+#define	ZFS_CONTEXT_OS_H_
+
+#define	HAVE_LARGE_STACKS	1
+
+#endif