Fix syntax error in makefile soong namespaces handling

Change-Id: I5254f7877422e23f3c3b69f37f1be849a12e296a
Signed-off-by: Alexey Polyudov <apolyudov@google.com>
diff --git a/core/product_config.mk b/core/product_config.mk
index 2cd8016..3cd2f23 100644
--- a/core/product_config.mk
+++ b/core/product_config.mk
@@ -482,7 +482,7 @@
     $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_CFI_INCLUDE_PATHS))
 
 # which Soong namespaces to export to Make
-PRODUCT_SOONG_NAMESPACES :=
+PRODUCT_SOONG_NAMESPACES := \
     $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SOONG_NAMESPACES))
 
 # A flag to override PRODUCT_COMPATIBLE_PROPERTY