meson: don't search PATH for telinit (#7770)

On a typical system running systemd, the telinit in PATH is very likely to be a symlink
to systemctl. Setting TELINIT to this may result in an infinite recursion if telinit is called
and sd_booted() == 0. This may commonly occur in a chroot environment.

Bug: https://bugs.gentoo.org/642724

[zj:
The path was originally hardcoded as "/lib/upstart/telinit", but was made configurable without
changing the default in 4ad61fd180. Then the default was
changed to `/lib/sysvinit/telinit` in abaaabf40a. Then it
started being  autodetected when meson support was added in 
5c23128dab. This patch restores the behaviour that was 
implemented in configure.ac at the time of its removal.]

meson.build

@@ -503,8 +503,7 @@ splash_bmp = files('test/splash.bmp')
 
 # if -Dxxx-path option is found, use that. Otherwise, check in $PATH,
 # /usr/sbin, /sbin, and fall back to the default from middle column.
-progs = [['telinit',    '/lib/sysvinit/telinit'],
-         ['quotaon',    '/usr/sbin/quotaon'    ],
+progs = [['quotaon',    '/usr/sbin/quotaon'    ],
          ['quotacheck', '/usr/sbin/quotacheck' ],
          ['kill',       '/usr/bin/kill'        ],
          ['kmod',       '/usr/bin/kmod'        ],
@@ -531,6 +530,8 @@ foreach prog : progs
         substs.set(name, path)
 endforeach
 
+conf.set_quoted('TELINIT', get_option('telinit-path'))
+
 if run_command('ln', '--relative', '--help').returncode() != 0
         error('ln does not support --relative')
 endif

meson_options.txt

@@ -29,7 +29,8 @@ option('sysvinit-path', type : 'string', value : '/etc/init.d',
        description : 'the directory where the SysV init scripts are located')
 option('sysvrcnd-path', type : 'string', value : '/etc/rc.d',
        description : 'the base directory for SysV rcN.d directories')
-option('telinit-path', type : 'string', description : 'path to telinit')
+option('telinit-path', type : 'string', value : '/lib/sysvinit/telinit',
+       description : 'path to telinit')
 option('rc-local', type : 'string',
        value : '/etc/rc.local')
 option('halt-local', type : 'string',