Fix Namespace Apple runner dispatch

Scripts/_burrow-flake.sh

@@ -27,7 +27,7 @@ burrow_prepare_flake_ref() {
   local resolved
   resolved="$(cd "${input}" && pwd)"
 
-  local cache_root="${HOME}/.cache/burrow"
+  local cache_root="${BURROW_FLAKE_CACHE_ROOT:-${HOME}/.cache/burrow}"
   mkdir -p "${cache_root}"
 
   local copy_root
@@ -37,6 +37,8 @@ burrow_prepare_flake_ref() {
   rsync -a \
     --delete \
     --exclude '.git' \
+    --exclude '.cache' \
+    --exclude '.derived-data' \
     --exclude '.direnv' \
     --exclude 'result' \
     --exclude 'burrow.sock' \