Make SK_FREETYPE_MINIMUM_RUNTIME_VERSION private.

The define SK_FREETYPE_MINIMUM_RUNTIME_VERSION is only used when
building Skia the library -- it does not affect any headers. As a
result, it should only be set when building Skia, it does not need
to be defined when building dependencies.

BUG=chromium:732670

Change-Id: I35eb988fb9e8af395e9f5d8668d7c0b3a5a02db8
Reviewed-on: https://chromium-review.googlesource.com/533573
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Ben Wagner <bungeman@google.com>
Cr-Commit-Position: refs/heads/master@{#479178}

skia/BUILD.gn

@@ -54,10 +54,6 @@ config("skia_config") {
     defines += [ "SK_HAS_JPEG_LIBRARY" ]
   }
 
-  if (!use_system_freetype) {
-    defines += [ "SK_FREETYPE_MINIMUM_RUNTIME_VERSION=(((FREETYPE_MAJOR) * 0x01000000) | ((FREETYPE_MINOR) * 0x00010000) | ((FREETYPE_PATCH) * 0x00000100))" ]
-  }
-
   if (is_component_build) {
     defines += [
       "SKIA_DLL",
@@ -128,6 +124,10 @@ config("skia_library_config") {
 
   defines = []
 
+  if (!use_system_freetype) {
+    defines += [ "SK_FREETYPE_MINIMUM_RUNTIME_VERSION=(((FREETYPE_MAJOR) * 0x01000000) | ((FREETYPE_MINOR) * 0x00010000) | ((FREETYPE_PATCH) * 0x00000100))" ]
+  }
+
   if (is_component_build) {
     defines += [ "SKIA_IMPLEMENTATION=1" ]
   }