fix breakage found by randomconfig

diff --git a/Makefile b/Makefile
index 37b6d9b..1bcf1e1 100644
--- a/Makefile
+++ b/Makefile
@@ -698,6 +698,8 @@
 else
 	$(Q)$(STRIP) -s --remove-section=.note --remove-section=.comment \
 		busybox_unstripped -o $@
+# strip is confused by PIE executable and does not set exec bits
+	$(Q)chmod a+x $@
 endif
 
 # The actual objects are generated when descending,