Only GN check //skia if checkout_skia=True

Drops dependency on //skia for GN checks unless the checkout_skia
gclient var is True. This fixes the build for gclient configurations
such as checkout_configuration=minimal.

Fixed: pdfium:1938
Change-Id: I280b5165925bc5f1a48a102236729fed467f4268
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/101151
Auto-Submit: K. Moon <kmoon@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: K. Moon <kmoon@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index 689ea87..070df30 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/clang/clang.gni")
+import("//build/config/gclient_args.gni")
 import("//testing/test.gni")
 import("pdfium.gni")
 
@@ -581,7 +582,7 @@
 
   # TODO(crbug.com/pdfium/1832): Remove !is_android when //third_party/expat is
   # available.
-  if (!is_android) {
+  if (checkout_skia && !is_android) {
     deps += [ "//skia" ]
   }
 }
diff --git a/DEPS b/DEPS
index 91900eb..6f14ac7 100644
--- a/DEPS
+++ b/DEPS
@@ -1,7 +1,9 @@
 use_relative_paths = True
 
 gclient_gn_args_file = 'build/config/gclient_args.gni'
-gclient_gn_args = []
+gclient_gn_args = [
+  'checkout_skia',
+]
 
 vars = {
   # By default, we should check out everything needed to run on the main