Make both SK_API definition points identical and order independent.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2189983002

Review-Url: https://codereview.chromium.org/2189983002
diff --git a/BUILD.gn b/BUILD.gn
index 7459fb0..d4ccf63 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -8,6 +8,7 @@
 
 skia_public_includes = [
   "include/android",
+  "include/c",
   "include/codec",
   "include/config",
   "include/core",
@@ -21,8 +22,6 @@
   "include/utils",
   "include/utils/mac",
   "include/xml",
-
-  "include/c",  # TODO: move back to top, order shouldn't matter
 ]
 
 # Skia public API, generally provided by :skia.