Make core/ pass gn check.

Use allow_circular_includes_from as a crutch for now.

Change-Id: Ia7a29a268e67b1fe21bed5cdd629e06fb5cc7bfb
Reviewed-on: https://pdfium-review.googlesource.com/c/43992
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fxcodec/BUILD.gn b/core/fxcodec/BUILD.gn
index 442a058..4c06d55 100644
--- a/core/fxcodec/BUILD.gn
+++ b/core/fxcodec/BUILD.gn
@@ -73,8 +73,10 @@
     "../../third_party:lcms2",
     "../../third_party:zlib",
     "../fxcrt",
+    "../fxge",
     "//third_party:jpeg",
   ]
+  allow_circular_includes_from = [ "../fxge" ]
 
   if (pdf_enable_xfa) {
     sources += [