busybox: use external libtirpc when using glibc

In recent glibc versions rpc functionality has been moved to a separate
library instead of glibc itself.
Depend on this library when rpc functionality is needed and glibc is
used.

Signed-off-by: Matthias Franck <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/17796
Signed-off-by: Hauke Mehrtens <[email protected]>
(cherry picked from commit 84e090086795a45d5580138436ce74b6170584ab)

package/utils/busybox/Makefile

@@ -48,7 +48,7 @@ define Package/busybox/Default
   MAINTAINER:=Felix Fietkau <[email protected]>
   TITLE:=Core utilities for embedded Linux
   URL:=http://busybox.net/
-  DEPENDS:=+BUSYBOX_CONFIG_PAM:libpam +BUSYBOX_CONFIG_NTPD:jsonfilter
+  DEPENDS:=+BUSYBOX_CONFIG_PAM:libpam +BUSYBOX_CONFIG_NTPD:jsonfilter +(USE_GLIBC&&BUSYBOX_CONFIG_FEATURE_MOUNT_NFS)||(USE_GLIBC&&BUSYBOX_CONFIG_FEATURE_INETD_RPC):libtirpc
   USERID:=ntp=123:ntp=123
 endef
 
@@ -104,6 +104,13 @@ ifeq ($(CONFIG_USE_GLIBC),y)
   LDLIBS += $(call BUSYBOX_IF_ENABLED,NSLOOKUP,resolv)
 endif
 
+ifneq ($(CONFIG_BUSYBOX_$(BUSYBOX_SYM)_FEATURE_MOUNT_NFS)$(CONFIG_BUSYBOX_$(BUSYBOX_SYM)_FEATURE_INETD_RPC),)
+ifndef CONFIG_USE_MUSL
+  TARGET_CFLAGS += -I$(STAGING_DIR)/usr/include/tirpc
+  LDLIBS += tirpc
+endif
+endif
+
 ifeq ($(BUILD_VARIANT),selinux)
   LDLIBS += selinux sepol
 endif