nix: move fetch-zig-cache script into nix/build-support

nix/build-support/check-zig-cache-hash.sh

@@ -34,7 +34,7 @@ trap 'rm -rf "${ZIG_GLOBAL_CACHE_DIR}"' EXIT
 
 # Run Zig and download the cache to the temporary directory.
 
-sh ./fetch-zig-cache.sh
+sh ./nix/build-support/fetch-zig-cache.sh
 
 # Now, calculate the hash.
 ZIG_CACHE_HASH="sha256-$(nix-hash --type sha256 --to-base64 "$(nix-hash --type sha256 "${ZIG_GLOBAL_CACHE_DIR}")")"

nix/package.nix

@@ -56,7 +56,7 @@
         ../vendor
         ../build.zig
         ../build.zig.zon
-        ../fetch-zig-cache.sh
+        ./build-support/fetch-zig-cache.sh
       ]
     );
   };
@@ -91,7 +91,7 @@
     buildPhase = ''
       runHook preBuild
 
-      sh ./fetch-zig-cache.sh
+      sh ./nix/build-support/fetch-zig-cache.sh
 
       runHook postBuild
     '';