sessreg: fix gcc6 build

srcpkgs/sessreg/template

@@ -21,6 +21,27 @@ case "$XBPS_TARGET_MACHINE" in
 		;;
 esac
 
+post_configure() {
+	local _gccver=$(gcc --version | awk '/^gcc \(GCC\)/ { print $3 }')
+	#
+	# gcc6 cpp fails to generate filenames.sed from filenames.sed.c
+	# thus we remove the buuld rule and provide a filenames.sed file
+	# with the expected output for Void Linux.
+	#
+	if [ "${_gccver%%.*}" -gt 5 ]; then
+		sed -i man/Makefile -e'/filenames.sed: filenames.sed.c/,+4d'
+		cat > man/filenames.sed << EOF
+/__BEGIN_UTMP_ONLY__/,/__END_UTMP_ONLY__/ d
+s|__utmp_manpage__|utmpx|g
+s|__utmp_file__|"/var/run/utmp"|g
+s|__wtmp_manpage__|wtmpx|g
+s|__wtmp_file__|"/var/log/wtmp"|g
+s|__ttys_file__|"/etc/ttys"|g
+s|__lastlog_file__|"/var/log/lastlog"|g
+EOF
+	fi
+}
+
 post_install() {
 	vlicense COPYING
 }