package/xvkbd: fix build with gcc >= 14.x

Fixes:

  https://autobuild.buildroot.net/results/86f2ba051e864375bda620dd92e01cb7b8532ac3/

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/xvkbd/0001-gcc-14.patch

@@ -0,0 +1,19 @@
+Fix build with gcc-14
+
+Upstream: https://sources.debian.org/src/xvkbd/4.1-3/debian/patches/gcc-14
+
+Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
+---
+ xvkbd.c |    1 +
+ 1 file changed, 1 insertion(+)
+
+--- a/xvkbd.c
++++ b/xvkbd.c
+@@ -15,6 +15,7 @@
+  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+  * See the GNU General Public License for more details.
+  */
++#define _CONST_X_STRING
+ #include <stdio.h>
+ #include <stdlib.h>
+ #include <unistd.h>