diff -rauN libcap-2.25/libcap/Makefile libcap-2.25-gperf-stddef-size_t-patch/libcap/Makefile
--- libcap-2.25/libcap/Makefile	2016-01-31 01:01:41.000000000 +0100
+++ libcap-2.25-gperf-stddef-size_t-patch/libcap/Makefile	2018-03-23 16:04:23.621999557 +0100
@@ -41,7 +41,7 @@
 	./_makenames > cap_names.h
 
 $(GPERF_OUTPUT): cap_names.list.h
-	perl -e 'print "struct __cap_token_s { const char *name; int index; };\n%{\nconst struct __cap_token_s *__cap_lookup_name(const char *, unsigned int);\n%}\n%%\n"; while ($$l = <>) { $$l =~ s/[\{\"]//g; $$l =~ s/\}.*// ; print $$l; }' < $< | gperf --ignore-case --language=ANSI-C --readonly --null-strings --global-table --hash-function-name=__cap_hash_name --lookup-function-name="__cap_lookup_name" -c -t -m20 $(INDENT) > $@
+	perl -e 'print "struct __cap_token_s { const char *name; int index; };\n%{\nconst struct __cap_token_s *__cap_lookup_name(const char *, unsigned int);\n%}\n%%\n"; while ($$l = <>) { $$l =~ s/[\{\"]//g; $$l =~ s/\}.*// ; print $$l; }' < $< | gperf --ignore-case --language=ANSI-C --readonly --null-strings --global-table --hash-function-name=__cap_hash_name --lookup-function-name="__cap_lookup_name" -c -t -m20 $(INDENT) | sed '3 a #include <stddef.h>' > $@
 
 cap_names.list.h: Makefile $(KERNEL_HEADERS)/linux/capability.h
 	@echo "=> making $@ from $(KERNEL_HEADERS)/linux/capability.h"