Make CustomizationPickerActivity can be overridden

Bug: 181756152
Test: Build; Manual
Change-Id: If8674cb413eba35c84543afe6980f1601d26b2dd
diff --git a/Android.bp b/Android.bp
index 755ba1d..68da5c5 100644
--- a/Android.bp
+++ b/Android.bp
@@ -64,6 +64,8 @@
         ":ThemePicker_srcs",
         "src_override/**/*.java",
         "src_override/**/*.kt",
+        "src_overridecustom/**/*.java",
+        "src_overridecustom/**/*.kt",
     ],
 
     use_embedded_native_libs: true,