Add GN build of DXC

Building dawn_native will build dxcompiler.dll, but it it not yet used.

Bug: dawn:1862
Change-Id: I3d821506657cd522dce8b183d45b44adf10ad232
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/138001
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 8c1db06..0a9da62 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -119,6 +119,7 @@
         "src/dawn/tests/end2end/DepthBiasTests.cpp",  # External URL
         "src/tint/transform/canonicalize_entry_point_io.cc",  # External URL
         "test/tint/samples/compute_boids.wgsl",  # External URL
+        "third_party/gn/dxc/BUILD.gn",  # Third party file
         "third_party/khronos/KHR/khrplatform.h",  # Third party file
         "tools/roll-all",  # Branch name
         "tools/src/container/key.go",  # External URL