Import posix_spawn from Gnulib.

posix_spawn is less error-prone than vfork + exec, and can make use of
system-specific optimizations like `clone' on Linux.  Import Gnulib
replacement so that we can use recent additions like
`posix_spawn_file_actions_addchdir'.

The only manual change are to admin/merge-gnulib and .gitignore.  All
other changes are due to rerunning merge-gnulib.

* admin/merge-gnulib (GNULIB_MODULES): Add posix_spawn-related
modules.
* .gitignore: Add new generated files.

1 files changed, 28 insertions, 0 deletions

diff --git a/lib/spawnattr_destroy.c b/lib/spawnattr_destroy.c
new file mode 100644
index 00000000000..22a7d5a61a2
--- /dev/null
+++ b/lib/spawnattr_destroy.c
@@ -0,0 +1,28 @@
+/* Copyright (C) 2000, 2009-2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <spawn.h>
+
+/* Initialize data structure for file attribute for 'spawn' call.  */
+int
+posix_spawnattr_destroy (posix_spawnattr_t *attr)
+{
+  /* Nothing to do in the moment.  */
+  return 0;
+}