ppp: Fix build when shadow is enabled

GCC-15 patch is not sufficient when shadow is enabled, therefore fix
the remaining issues.

(From OE-Core rev: 9143b23cecb505f130f86b03039c6c0aba5dcc2b)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-connectivity/ppp/ppp/0001-pppd-session-Fixed-building-with-GCC-15.patch

@@ -0,0 +1,33 @@
+From 5edcb01f1d8d521c819d45df1f1bb87697252130 Mon Sep 17 00:00:00 2001
+From: Khem Raj <raj.khem@gmail.com>
+Date: Mon, 17 Mar 2025 14:38:26 -0700
+Subject: [PATCH] pppd/session: Fixed building with GCC 15
+
+Fixed building with GCC 15 which defaults to C23
+and find conflicting declration of getspnam() here
+with the one provided by shadow.h (extern struct spwd *getspnam (const char *__name);)
+
+Fixes
+../../ppp-2.5.2/pppd/session.c: In function 'session_start':
+../../ppp-2.5.2/pppd/session.c:185:18: error: conflicting types for 'getspnam'; have 'struct spwd *(void)'
+  185 |     struct spwd *getspnam();
+      |                  ^~~~~~~~
+
+Upstream-Status: Submitted [https://github.com/ppp-project/ppp/pull/553]
+Signed-off-by: Khem Raj <raj.khem@gmail.com>
+---
+ pppd/session.c | 1 -
+ 1 file changed, 1 deletion(-)
+
+diff --git a/pppd/session.c b/pppd/session.c
+index f08d8e1..9cc7538 100644
+--- a/pppd/session.c
++++ b/pppd/session.c
+@@ -182,7 +182,6 @@ session_start(const int flags, const char *user, const char *passwd, const char
+     char *cbuf;
+ #ifdef HAVE_SHADOW_H
+     struct spwd *spwd;
+-    struct spwd *getspnam();
+     long now = 0;
+ #endif /* #ifdef HAVE_SHADOW_H */
+ #endif /* #ifdef PPP_WITH_PAM */

meta/recipes-connectivity/ppp/ppp_2.5.2.bb

@@ -25,6 +25,7 @@ SRC_URI = "https://download.samba.org/pub/${BPN}/${BP}.tar.gz \
            file://ppp@.service \
            file://0001-pppdump-Fixed-building-with-GCC-15-548.patch \
            file://0001-pppd-pppdconf.h-remove-erroneous-generated-header.patch \
+           file://0001-pppd-session-Fixed-building-with-GCC-15.patch \
            "
 
 SRC_URI[sha256sum] = "47da358de54a10cb10bf6ff2cf9b1c03c0d3555518f6182e8f701b8e55733cb2"