move gpu_tool_utils to public_deps

This "fixes" the situation where targets know they want
to link MacOS frameworks like MoltenVK (-framework), but
don't know where to find them (-F).

It's not totally clear to me that this is a principled
fix, but it does make things build.

Change-Id: I018251cad129acb1a176ccce056caa131ee70789
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/203687
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index fee71a8..7ee1d9b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1657,6 +1657,8 @@
     deps = [
       ":experimental_svg_model",
       ":flags",
+    ]
+    public_deps = [
       ":gpu_tool_utils",
     ]
   }