package/chocolate-doom: fix build with gcc 10

Fixes:
 - http://autobuild.buildroot.org/results/02828f2d9956d1e3727774b5045790aa3611428d

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/chocolate-doom/0001-Remove-redundant-demoextend-definition.patch

@@ -0,0 +1,29 @@
+From a8fd4b1f563d24d4296c3e8225c8404e2724d4c2 Mon Sep 17 00:00:00 2001
+From: Jordan Christiansen <xordspar0@gmail.com>
+Date: Sun, 15 Mar 2020 16:55:33 -0500
+Subject: [PATCH] Remove redundant demoextend definition
+
+GCC 10 enables -fno-common by default, which causes the linker to fail when
+there are multple definitions of a global variable.
+
+See https://gcc.gnu.org/gcc-10/porting_to.html
+
+[Retrieved from:
+https://github.com/chocolate-doom/chocolate-doom/commit/a8fd4b1f563d24d4296c3e8225c8404e2724d4c2]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ src/hexen/mn_menu.c | 1 -
+ 1 file changed, 1 deletion(-)
+
+diff --git a/src/hexen/mn_menu.c b/src/hexen/mn_menu.c
+index 059f45b3e..a97b7fcd1 100644
+--- a/src/hexen/mn_menu.c
++++ b/src/hexen/mn_menu.c
+@@ -131,7 +131,6 @@ boolean MenuActive;
+ int InfoType;
+ int messageson = true;
+ boolean mn_SuicideConsole;
+-boolean demoextend; // from h2def.h
+ 
+ // PRIVATE DATA DEFINITIONS ------------------------------------------------
+