meson: Turn selinux into a meson feature and make it auto by default

Making it more user friendly when building on distro no deploying selinux

meson.build

@@ -1812,9 +1812,10 @@ if host_system == 'windows'
 endif
 
 selinux_dep = []
-if host_system == 'linux' and get_option('selinux')
-  selinux_dep = [dependency('libselinux')]
-  glib_conf.set('HAVE_SELINUX', 1)
+if host_system == 'linux'
+  selinux_dep = dependency('libselinux', required: get_option('selinux'))
+
+  glib_conf.set('HAVE_SELINUX', selinux_dep.found())
 endif
 
 xattr_dep = []

meson_options.txt

@@ -20,8 +20,8 @@ option('gio_module_dir',
        description : 'load gio modules from this directory (default to \'libdir/gio/modules\' if unset)')
 
 option('selinux',
-       type : 'boolean',
-       value : true,
+       type : 'feature',
+       value : 'auto',
        description : 'build with selinux support')
 
 option('xattr',