Bug 1385797 - Build activity-stream everywhere but keep preffed on only in Nightly. r=mossop

--HG--
extra : rebase_source : 59639a30d57345c8f8bea362f5b518b0e3703812

browser/extensions/moz.build

@@ -5,6 +5,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 DIRS += [
+    'activity-stream',
     'aushelper',
     'clicktoplay-rollout',
     'e10srollout',
@@ -36,9 +37,3 @@ if CONFIG['MOZ_MORTAR']:
     DIRS += [
         'mortar',
     ]
-
-# Nightly-only system add-ons
-if CONFIG['NIGHTLY_BUILD']:
-    DIRS += [
-        'activity-stream',
-    ]