gopher64: fix build (#462346)

pkgs/by-name/go/gopher64/allow-unused-type.patch

@@ -0,0 +1,12 @@
+diff --git a/src/device/cart.rs b/src/device/cart.rs
+index 97bf09f..4406fec 100644
+--- a/src/device/cart.rs
++++ b/src/device/cart.rs
+@@ -21,6 +21,7 @@ const JDT_EEPROM_16K: u16 = 0xc000; /* 16k EEPROM */
+ const EEPROM_BLOCK_SIZE: usize = 8;
+ pub const EEPROM_MAX_SIZE: usize = 0x800;
+ 
++#[allow(warnings)]
+ #[derive(serde::Serialize, serde::Deserialize)]
+ pub enum CicType {
+     CicNus6101,

pkgs/by-name/go/gopher64/package.nix

@@ -42,6 +42,9 @@ rustPlatform.buildRustPackage (finalAttrs: {
 
     # make the build script use the @GIT_REV@ string that will be substituted in the logic below
     ./set-git-rev.patch
+
+    # enum CicType is not used, but dead code is treated as an error
+    ./allow-unused-type.patch
   ];
 
   postPatch = ''