1) On FreeBSD X is normally started on VT9.
2) The shutdown command uses '-p' and not '-P' on FreeBSD.

--- CMakeLists.txt.orig	2017-12-05 16:00:16 UTC
+++ CMakeLists.txt
@@ -168,8 +168,8 @@ add_feature_info("elogind" ELOGIND_FOUND "elogind supp
 
 # Default behaviour if neither systemd nor elogind is used
 if (NOT ELOGIND_FOUND AND NOT SYSTEMD_FOUND)
-    set(MINIMUM_VT 7)
-    set(HALT_COMMAND "/sbin/shutdown -h -P now")
+    set(MINIMUM_VT 9)
+    set(HALT_COMMAND "/sbin/shutdown -p now")
     set(REBOOT_COMMAND "/sbin/shutdown -r now")
 endif()