fix: use matching flutter linux bundle arch

tools/build-linux-deb.sh

@@ -51,6 +51,17 @@ resolve_arch() {
   esac
 }
 
+flutter_linux_arch() {
+  case "$1" in
+    amd64) echo "x64" ;;
+    arm64) echo "arm64" ;;
+    *)
+      echo "ERROR: unsupported Flutter Linux architecture '$1'" >&2
+      exit 1
+      ;;
+  esac
+}
+
 main() {
   require_cmd flutter
   require_cmd dpkg-deb
@@ -83,6 +94,8 @@ EOF
 
   local arch
   arch="$(resolve_arch)"
+  local flutter_arch
+  flutter_arch="$(flutter_linux_arch "$arch")"
 
   (
     cd "$APP_DIR"
@@ -90,7 +103,7 @@ EOF
     flutter build linux --release
   )
 
-  local bundle_dir="$APP_DIR/build/linux/x64/release/bundle"
+  local bundle_dir="$APP_DIR/build/linux/$flutter_arch/release/bundle"
   local app_binary="$bundle_dir/chanora_flutter"
   require_file "$app_binary" "Linux release bundle binary"