PRODUCT_BOOT_JARS as a list of jar names separated by space

This makes it easier for OEMs to extend the PRODUCT_BOOT_JARS in their
product configuration files.

Change-Id: I5feca2f808b1914c275f28c7a4c38cca2ba6851f
diff --git a/core/product_config.mk b/core/product_config.mk
index a2be30b..0574c66 100644
--- a/core/product_config.mk
+++ b/core/product_config.mk
@@ -280,7 +280,7 @@
 #############################################################################
 
 # A list of module names of BOOTCLASSPATH (jar files)
-PRODUCT_BOOT_JARS := $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_BOOT_JARS)
+PRODUCT_BOOT_JARS := $(strip $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_BOOT_JARS))
 
 # Find the device that this product maps to.
 TARGET_DEVICE := $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_DEVICE)