fix(build): variables in @site.variables were ignored

If the component uses the default theme, any changes to site.variables in @{themesFolder}/@{site}/globals/site.variables are ignored.

Additionally site.variables now trigger a rebuild.

Closes
#1003

src/theme.less

@@ -19,7 +19,9 @@
 @import (optional) "@{themesFolder}/@{site}/globals/site.variables";
 
 /* Component's site.variables */
-@import (optional) "@{themesFolder}/@{theme}/globals/site.variables";
+& when not (@theme = 'default') {
+  @import (optional) "@{themesFolder}/@{theme}/globals/site.variables";
+}
 
 /* Site theme site.variables */
 @import (optional) "@{siteFolder}/globals/site.variables";

tasks/build/css.js

@@ -194,7 +194,8 @@ module.exports.watch = function (type, config) {
   // Watch theme.config file
   gulp.watch([
     normalize(config.paths.source.config),
-    normalize(config.paths.source.site + '/**/site.variables')
+    normalize(config.paths.source.site + '/**/site.variables'),
+    normalize(config.paths.source.themes + '/**/site.variables')
   ])
     .on('all', function () {
       // Clear timeout and reset files