Probe for the existence of FIFREEZE and make fsfreeze depend on it.
diff --git a/toys/other/fsfreeze.c b/toys/other/fsfreeze.c
index f7b8a94..e169554 100644
--- a/toys/other/fsfreeze.c
+++ b/toys/other/fsfreeze.c
@@ -7,6 +7,7 @@
 config FSFREEZE
   bool "fsfreeze"
   default y
+  depends on TOYBOX_FIFREEZE
   help
     usage: fsfreeze {-f | -u} MOUNTPOINT