Make fpdfsdk/ pass gn check.

Use allow_circular_includes_from as a crutch for now.

Change-Id: I58e90da4b71a22dd54fd59e8d644b6eef740d4cd
Reviewed-on: https://pdfium-review.googlesource.com/c/43988
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/.gn b/.gn
index 1d4f5fc..764e08c 100644
--- a/.gn
+++ b/.gn
@@ -18,6 +18,7 @@
 
 check_targets = [
   "//core/fxcrt/*",
+  "//fpdfsdk/*",
   "//fxbarcode/*",
   "//samples/*",
   "//testing/:*",
@@ -27,6 +28,5 @@
 
   # TODO(thestig): Work on these.
   #"//core/*",
-  #"//fpdfsdk/*",
   #"//fxjs/*",
 ]