gzdoom: only build for 64-bit architectures

Only LP64/LLP64 builds are officially supported. Please do not attempt
to build for other platforms; even if the program succeeds in a MAP01
smoke test, there are e.g. known visual artifacts that lead to a bad
user experience.

Link: https://forum.zdoom.org/viewtopic.php?f=7&t=75673
Signed-off-by: Daniel Golle <daniel@makrotopia.org>

games/gzdoom/Makefile

@@ -37,7 +37,7 @@ define Package/gzdoom
   CATEGORY:=Games
   TITLE:=GZDoom
   URL:=https://zdoom.org/
-  DEPENDS:=+alsa-lib +glib2 +libbz2 +libstdcpp +libzmusic +libvpx +libsdl2 +USE_MUSL:musl-fts
+  DEPENDS:=+alsa-lib +glib2 +libbz2 +libstdcpp +libzmusic +libvpx +libsdl2 +USE_MUSL:musl-fts @ARCH_64BIT
 endef
 
 define Package/gzdoom/description