package/docker: Fix build with gcc-15.x

Add patch from Debian to fix build error with gcc-15.x

Fixes:
https://autobuild.buildroot.net/results/495/4956555fd033d43c1877e66141789bcd06aff5be/

Patch sent to fork which is used by Arch Linux:
https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=wmdocker

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Julien Olivain <ju.o@free.fr>
(cherry picked from commit cc3647e73f)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>

package/docker/0001-fix-gcc-15-compatibility-explicit-fallthrough-undecl.patch

@@ -0,0 +1,38 @@
+From 55054532589041e3c7b970fefaeeeee871f4f6be Mon Sep 17 00:00:00 2001
+From: Tianon Gravi <tianon@debian.org>
+Date: Wed, 25 Feb 2026 08:24:26 +0100
+Subject: [PATCH] fix gcc-15+ compatibility (explicit fallthrough,
+ undeclared/unused arguments)
+
+Downloaded from Debian:
+https://sources.debian.org/src/docker/1.5-6/debian/patches/gcc-15.patch
+
+Upstream: https://github.com/mdomlop/wmdocker/commit/55054532589041e3c7b970fefaeeeee871f4f6be
+
+[Bernd: rebased patch]
+Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
+---
+ docker.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/docker.c b/docker.c
+index 4cc8d78..6105ab8 100644
+--- a/docker.c
++++ b/docker.c
+@@ -46,7 +46,7 @@ void signal_handler(int signal)
+ }
+ 
+ 
+-void parse_cmd_line()
++void parse_cmd_line(int argc, char **argv)
+ {
+   int i;
+   gboolean help = FALSE;
+@@ -283,6 +283,7 @@ void event_loop()
+       case ReparentNotify:
+         if (e.xany.window == win) /* reparented to us */
+           break;
++        /* fallthrough */
+       case UnmapNotify:
+       case DestroyNotify:
+         for (it = icons; it; it = g_slist_next(it)) {