Update the gradle build tasks to generate play store builds.

Configure the gradle builds to sign and build the release version of the Godot Android Editor

platform/android/detect.py

@@ -22,6 +22,8 @@ def can_build():
 
 
 def get_opts():
+    from SCons.Variables import BoolVariable
+
     return [
         ("ANDROID_SDK_ROOT", "Path to the Android SDK", get_env_android_sdk_root()),
         (
@@ -29,6 +31,7 @@ def get_opts():
             'Target platform (android-<api>, e.g. "android-' + str(get_min_target_api()) + '")',
             "android-" + str(get_min_target_api()),
         ),
+        BoolVariable("store_release", "Editor build for Google Play Store (for official builds only)", False),
     ]