Fix skottie_tool build

Should be guarded by the Skottie build flag.

Change-Id: I4e895a3759d19248fe0770dce710a0ef78c780b7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/417007
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@google.com>
Auto-Submit: Florin Malita <fmalita@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 38f6226..2aefdaf 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2072,8 +2072,10 @@
   }
 
   if (is_linux || is_mac) {
-    test_app("skottie_tool") {
-      deps = [ "modules/skottie:tool" ]
+    if (skia_enable_skottie) {
+      test_app("skottie_tool") {
+        deps = [ "modules/skottie:tool" ]
+      }
     }
     test_app("svg_tool") {
       deps = [ "modules/svg:tool" ]