Improve public header file checking

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index a07e2e29f54363499d8614b4a1074819f52f59fe..515ce8fb13139628d07798449258aad37da25c91 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -32,7 +32,6 @@ group("root") {
     #"//sdch",
     #"//skia",
     #"//third_party/WebKit/Source/platform",
-    "//third_party/freetype2",
     #"//third_party/icu:icudata",
     #"//third_party/leveldatabase",
     "//third_party/libpng",
@@ -42,4 +41,10 @@ group("root") {
     "//tools/gn",
     "//url",
   ]
+
+  if (is_linux) {
+    deps += [
+      "//third_party/freetype2",
+    ]
+  }
 }