meson: place systemd-sulogin-shell in build/

We do that will all executables so that it's easy to call them.

src/sulogin-shell/meson.build

@@ -1,25 +0,0 @@
-# SPDX-License-Identifier: LGPL-2.1+
-#
-# Copyright 2017 Zbigniew Jędrzejewski-Szmek
-#
-# systemd is free software; you can redistribute it and/or modify it
-# under the terms of the GNU Lesser General Public License as published by
-# the Free Software Foundation; either version 2.1 of the License, or
-# (at your option) any later version.
-#
-# systemd 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
-# Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with systemd; If not, see <http://www.gnu.org/licenses/>.
-
-executable('systemd-sulogin-shell',
-           ['sulogin-shell.c'],
-           include_directories : includes,
-           link_with : [libshared],
-           dependencies : [],
-           install_rpath : rootlibexecdir,
-           install : true,
-           install_dir : rootlibexecdir)