Add the ability in a product spec file to have modules installed for specific variants.

Change-Id: Ifa5eb2e15b3d3e5007378ec00efc4aec3e9a3b99
diff --git a/core/product.mk b/core/product.mk
index 283b6ef..5d421de 100644
--- a/core/product.mk
+++ b/core/product.mk
@@ -66,6 +66,9 @@
     PRODUCT_AAPT_CONFIG \
     PRODUCT_AAPT_PREF_CONFIG \
     PRODUCT_PACKAGES \
+    PRODUCT_PACKAGES_DEBUG \
+    PRODUCT_PACKAGES_ENG \
+    PRODUCT_PACKAGES_TESTS \
     PRODUCT_DEVICE \
     PRODUCT_MANUFACTURER \
     PRODUCT_BRAND \