[core] Fixed codegen script

Updated path to style spec reference following spinoff from gl-native repository. Centralized overrides for not-yet-implemented layout properties. Removed overrides that have already been removed for mbgl in gl-native.

scripts/generate-style-code.js

@@ -6,11 +6,6 @@ const ejs = require('ejs');
 const spec = require('./style-spec');
 const colorParser = require('csscolorparser');
 
-// FIXME: https://github.com/mapbox/mapbox-gl-native/issues/15008
-delete spec.layout_circle["circle-sort-key"]
-delete spec.layout_line["line-sort-key"]
-delete spec.layout_fill["fill-sort-key"]
-
 require('./style-code');
 
 function parseCSSColor(str) {

scripts/style-spec.js

@@ -1 +1,4 @@
-var spec = module.exports = require('../mapbox-gl-js/src/style-spec/reference/v8');
+var spec = module.exports = require('../vendor/mapbox-gl-native/mapbox-gl-js/src/style-spec/reference/v8');
+
+// FIXME: https://github.com/mapbox/mapbox-gl-native/issues/15008
+delete spec.layout_circle["circle-sort-key"];