even more fixes from randomconfig runs

diff --git a/libbb/Kbuild b/libbb/Kbuild
index c6c33bd..87cc698 100644
--- a/libbb/Kbuild
+++ b/libbb/Kbuild
@@ -125,5 +125,6 @@
 lib-$(CONFIG_EXPR) += xregcomp.o
 lib-$(CONFIG_MDEV) += xregcomp.o
 lib-$(CONFIG_LESS) += xregcomp.o
+lib-$(CONFIG_PGREP) += xregcomp.o
 lib-$(CONFIG_DEVFSD) += xregcomp.o
 lib-$(CONFIG_FEATURE_FIND_REGEX) += xregcomp.o