Update chocolate-doom-system.sh

changing to a older commit so it can compile

Author: Exarkuniv

scriptmodules/ports/chocolate-doom-system.sh

@@ -14,7 +14,7 @@ rp_module_id="chocolate-doom-system"
 rp_module_desc="Chocolate Doom - Enhanced port of the official DOOM source"
 rp_module_licence="GPL2 https://raw.githubusercontent.com/chocolate-doom/chocolate-doom/sdl2-branch/COPYING"
 rp_module_help="Please add your iWAD files to $romdir/ports/doom/ with filenames in lowercase. Run 'chocolate-doom-setup' to configure your controls and options."
-rp_module_repo="git https://github.com/chocolate-doom/chocolate-doom.git master"
+rp_module_repo="git https://github.com/chocolate-doom/chocolate-doom.git master 640de9f"
 rp_module_section="exp"
 rp_module_flags="!mali !x86"
 
@@ -78,4 +78,4 @@ function configure_chocolate-doom-system() {
     [[ "$md_mode" == "install" ]] && game_data_chocolate-doom-system
     [[ "$md_mode" == "remove" ]] && return
 
-}
+}