we were basically ignoring CONFIG_USE_BB_PWD_GRP (assuming =y),
fix this
diff --git a/libpwdgrp/Kbuild b/libpwdgrp/Kbuild
index 9e60ef1..f9f1ddb 100644
--- a/libpwdgrp/Kbuild
+++ b/libpwdgrp/Kbuild
@@ -4,4 +4,6 @@
 #
 # Licensed under the GPL v2, see the file LICENSE in this tarball.
 
-lib-y:=pwd_grp.o uidgid_get.o
+lib-y := uidgid_get.o
+
+lib-$(CONFIG_USE_BB_PWD_GRP) += pwd_grp.o