GN: quiet link.exe warning spam.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4448

Change-Id: Iabc76cf111a62783770725a6cbf3a4284f35502b
Reviewed-on: https://skia-review.googlesource.com/4448
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
diff --git a/gn/BUILD.gn b/gn/BUILD.gn
index a39217e..83d2733 100644
--- a/gn/BUILD.gn
+++ b/gn/BUILD.gn
@@ -401,6 +401,11 @@
       "-rdynamic",
       "-Wl,-rpath,\$ORIGIN",
     ]
+  } else if (is_win) {
+    ldflags = [
+      "/SUBSYSTEM:CONSOLE",  # Quiet "no subsystem specified; CONSOLE assumed".
+      "/INCREMENTAL:NO",  # Quiet warnings about failing to incrementally link by never trying to.
+    ]
   }
 }