Make libpam optional

meson.build

@@ -40,7 +40,7 @@ gdk_pixbuf     = dependency('gdk-pixbuf-2.0', required: false)
 pixman         = dependency('pixman-1')
 libcap         = dependency('libcap', required: false)
 libinput       = dependency('libinput', version: '>=1.6.0')
-libpam         = cc.find_library('pam')
+libpam         = cc.find_library('pam', required: false)
 systemd        = dependency('libsystemd', required: false)
 elogind        = dependency('libelogind', required: false)
 math           = cc.find_library('m')
@@ -133,10 +133,13 @@ subdir('swaymsg')
 subdir('client')
 subdir('swaybg')
 subdir('swaybar')
-subdir('swaylock')
 subdir('swayidle')
 subdir('swaynag')
 
+if libpam.found()
+    subdir('swaylock')
+endif
+
 config = configuration_data()
 config.set('sysconfdir', join_paths(prefix, sysconfdir))
 config.set('datadir', join_paths(prefix, datadir))